Reading Guitar chords diagrams

There are 5 different methods. To make it clear, we will explain each of these methods using for instance a chord of A minor (Am).
 

Method #1 (tab) :

--0--
--1--
--2--
--2--
--0--
-----

This is the typical method based on the principle of the tab: The 6 lines represent the 6 guitar strings, the thickest string is the lowest line (the 6th), the thinnest is the first line (which finally makes sense because remember that the strings are counted from the thinnest to the thickest! therefore the thickest string is the 6th, represented here by the 6th line ...).
The numbers are here to indicate the frets where to put your fingers, 0 indicating that you have to pick the appropriate open string (i.e. without putting your finger on it).

Concretely in this example you must:

1. Pick the thinnest open string (the '0 'on the 1st line)

2. Put a finger on the fret 1 of the 2nd thinnest string (the '1' on the 2nd line)

3. Put another finger on the fret 2 of the 3rd string (the '2' on the 3rd line)

4. Put another finger on the fret 2 of the 4th string (the '2 ' on the 4th line)

5. Play open the 5th string ('0' on the 5th line)

6. Do not worry about the thick string (nothing is indicated on the 6th line, so we don't do anything!)

Method #2 (Chord diagram) :

o |---|---|---|
  |-x-|---|---|
  |---|-x-|---|
  |---|-x-|---|
o |---|---|---|
  |---|---|---|

This method is the most visual of all, so it's probably the easiest to understand, but unfortunately this method is far from being the most used (on the internet particularly).

It's a kind of aerial photo of your fretboard. The view is what you could have by putting your guitar on the floor in front of you, the fretboard on the left side, the soundbox (where you pick) on the right side. The lines represent the guitar strings (the thinnest at the top, the thickest at the bottom), the 'x' indicate where to put your fingers while the vertical columns define the frets of the guitar. The 'o' indicate if there are open strings to play.
The result to obtain is the same as above.

Method #3 (variant of the 2nd> method):

o |---|---|---|
  |-1-|---|---|
  |---|-3-|---|
  |---|-2-|---|
o |---|---|---|
  |---|---|---|

It's about the method 2 where an additional indication was provided: the individual position of each finger.
1 = index, 2 = middle, 3 = ring, 4 = little (not used here in this case)

Method #4 :

Am = x02210 

This method is the same as that of the tab (Method # 1) except that the lines of the tab was rotated 90 degrees in the direction of clockwise. So the thinnest string is on the right side and the thickest string on the left side. The 'X' mean that we do not deal with this particular string.

Method #5(variant of the 4th method)

EADGBe
------
x02210

It's the same technique as the method 3 with the names of the strings shown on it.