Can someone please explain it to me?
After all of these years, I have yet to fully understand what the Magisterium is and how it functions?
Is the Magisterium a group of people or a group of Church docuмents?
Also, What does the Magisterium have to do with the crisis in the Church and the N.O. Mass?

You are to be commended for asking this question. You are not alone in your confusion which imo, is everywhere and is rooted in certain false teachings of certain "well respected" 19th/20th century theologians.

A few minutes ago I made this list for another poster, perhaps you're him? It is by no means complete, just a quick reference list is all. At any rate, I hope it helps.

The Church is Christ’s Mystical Body, is Christ.

The Pope is Christ’s Vicar on earth, the Church’s visible Head, Her spokesman and the successor of St. Peter.

The Hierarchy is the Pope and Bishops, we often include Cardinals and priests.  

The Deposit of Faith is all revealed truths given by Christ and the Holy Ghost to His Church through the Apostles. These truths exist in written word, Scripture and unwritten traditions.

The Magisterium is the Church authoritatively teaching all those truths contained in the Deposit of Faith.

Ordinary Magisterium is the Church teaching in her usual, day to day activities.

Universal Magisterium is infallible, binding teachings that the Church has taught always and everywhere since the time of the Apostles.

Extraordinary Magisterium or Solemn Magisterium is the Church teaching in an unusual manner, such as through a Council or an ex cathedra statement made by the pope.

Ex Cathedra is the pope solemnly defining a doctrine or doctrines concerning faith or morals, binding on the whole Church. This is infallible teaching, being protected by the Holy Ghost, is divinely guaranteed to be without the possibility of error.

Infallibility is freedom from error in teaching the Universal Church in matters of faith or morals, as defined by the First Vatican Council (see “infallible teachings” below).

Infallible teachings are all those teachings contained in the Deposit of Faith, which are contained in the word of God as found in Scripture and tradition and which are proposed by the Church as matters to be believed as divinely revealed, whether by her solemn judgment or in her Ordinary Magisterium and Universal Magisterium.

Indefectibility is the fact that the Church in its faith and morals and its infallible interpretation will remain unchangeable until the end of time. It is that attribute of the Church by which it will remain until the end of time essentially the same as it was established by Christ.
 
 Impeccability is the impossibility of sinning.

However, neither the ordinary nor extraordinary magisterium are exercised during a period of interregnum, which is what we've been enduring for the last 50 years or so. So in practice for contemporary Catholics, it can be very challenging to understand the magisterium-- we've not lived with it.

Which is to say the Church ceases to teach between the death/abdication of the previous pope and the election of the new pope. Amazing.

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Properly speaking, both types of magisterium are infallible, but in each case their infallibility rests with the pope. No Pope, no infallibility.
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Bishops still teach during such periods, of course. But they enjoy no infallibility, even in consensus, because the source of ordinary infallibility is removed.
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So yes, as you can see, the Church is severely wounded without a Pope. Ergo the urgency with which she has always elected a new one, even from her earliest days.

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This was interesting to read, and well done by Mithrandylan and Stubborn. 
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I would like to add for newcomers to the concept that the word  Magisterium  is a Latin word, literally meaning the Teaching Office of the Church. (As already mentioned.)
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In Latin, a teaching office is neither male nor female; it has no gender. In Latin a person is either male or female, and cannot be neuter. That's the way Latin is. If the word were male, it would be "Magisterio" and if female, "Magisteria" or "Magisteriae." Since Magisterium is neither male nor female, it cannot apply to a person. Consequently it makes more sense to see that Magisterium cannot refer to one man or a group of men who hold office in the Church. Since Vat.II it has become commonplace for the word to be misunderstood in this way and it would seem there has been a deliberate effort of Modernists to inject a new meaning into the word. The use of the phrase "living Magisterium" is another aspect of this deception, by which the living Magisterium can change from day to day or over time, depending on the whims of the current occupants of the authoritative office in question.
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It helps to know that in Latin there are nouns that can be either male or female in specific cases, and when that happens the male gender is used, never the female, even though in a specific case the male gender noun could be applying to a female person. This concept is entirely lost on modern day feminism activists who have rebelled against this principle, accusing our ancestors of having a sexist agenda opposed to the good of women (literally, the female sex). Therefore when traditional literature says "mankind" or "God gave something to man," it applies equally to men and women and children. 
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Notice we do have a universal word for boys and girls (children), and we have "people" for males and females of all ages. But we would have to say "adults" for men and women without distinction. There is something poetic lost in the translation when "man" is replaced with "a person," and "mankind" is replaced with "people." 
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Then, "One small step for man, one giant leap for mankind" would become, "One small step for a person, one giant leap for people." Kind of falls flat, no?
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It helps to know that in Latin, there are three genders for nouns. That means that words have different ending letters that reflect which gender applies: male, female or neuter. In this case the letters "-ium" are the key indicators of the gender that applies, because Latin nouns ending in "-ium" are neuter gender, which is necessarily neither male nor female. Other languages, even Romance languages (based on Latin derivatives) apply gender to all nouns, for example Spanish, in which is found female tables (la mesa), chairs (la silla), houses (la casa) and geographical features (la ciudad); while male political offices (el presidente), tools (los hermientos), weapons (el navajo), and some mechanical components (el alambre). There are entities in Spanish that can be either male OR female, such as weather patterns (El Nino, or La Nina).
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Doesn't anyone just look things up and study anymore?

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There are laymen running websites who think it's their "vocation" (because of Vatican II) and they believe that the magisterium is a group of men in charge of telling people what to believe -- which can change from day to day. Why study when you already know the answer? If you try to explain to these guys what they're missing they get upset and don't believe what you tell them.
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There are laymen running websites who think it's their "vocation" (because of Vatican II) and they believe that the magisterium is a group of men in charge of telling people what to believe -- which can change from day to day. Why study when you already know the answer? If you try to explain to these guys what they're missing they get upset and don't believe what you tell them.
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Catholic Answers with their proof texts comes to mind.

Yes, excellent post.

I was just reading one of my favorite encyclicals, Satis Cognitum by Pope Leo XIII, and the phrase "living magisterium" is right there - no question a traditional and essential concept, and considered in relation to indefectibility, provides a grounding which helps understand and comes to terms with this crisis.  

Satis Cognitum:

Wherefore, as appears from what has been said, Christ instituted in the Church a living, authoritative and permanent Magisterium - [read: Teachings] which by His own power He strengthened, by the Spirit of truth He taught, and by miracles confirmed. He willed and ordered, under the gravest penalties, that its teachings should be received as if they were His own. As often, therefore, as it is declared on the authority of this teaching that this or that is contained in the deposit of divine revelation, it must be believed by every one as true. If it could in any way be false, an evident contradiction follows; for then God Himself would be the author of error in man. "Lord, if we be in error, we are being deceived by Thee". In this wise, all cause for doubting being removed...

The "living, authoritative and permanent Magisterium" Pope Leo XIII speaks of, is teachings. What it is not, is "all the bishops throughout the world teaching in union with the pope" past, present or future tense. Magisterium is not people, it's teachings.