pls help, teaching myself, i hope

Hey there! Yeah so i am trying to teach myself to but i took a short enough class to now enough. For you question about the cords...i don't think that you can change them but i am not 100% sure. About reading tab though...which is what i believe you questioned had the "numbers". Well, those numbers tell you which fret you are playing. For example, if it says one you play fret one or if there is five you play that fret...etc.

Thank you so much topdown!

e-------------------------------------------------------------------------------|
B------------------------15------------------------------15sl 17-15~~-13-12-----|
G-12--14b(16)rb14p 12-14---14b(16)rb14-12-12----------12------------------------|
D---------------------------------------------12sl 14---------------------------|
A-------------------------------------------------------------------------------|
E----

what do those number mean?

can you make any chord on any fret?  such as a c on the third fret and fifth fret?

The numbers are the strings to pick.

EG.

1----
--3--
----5
----
----
----

Would mean that you pick string 1 (e) with you pressing down the first fret.
Then the 3 on string 2 is the same, but you press on the 3rd fret. Tab is really easy to read when you know how.

As for Chords and frets, no a C is not a C if you move it along. A good way to show this is thus:

Let me entertain you (Robbie Williams) is a simple E-G-A-E (4/4 1+2+3+4+)
You can play it simple

E    G    A   E
0    3    0    0
0    0    2    0
1    0    2    1
2    0    2    2
2    2    0    2
0    3    0    0

OR you can make an Emaj, The if you slide it down one fret, it becomes a F, slide it down another its an F#. slide it down one more fret and you get a G. So you can strum Ex4, then slide it down 3 Frets, and strum four times on the G. Next is an A, so one more fret down and you have a G#, then one more fret and you have an A.

So you can play the whole song, by just sliding your fingers down the fret board changing the frets. It works on the musical alphabet.

   b           d        e       g       a
A A# B C C# D D# E F F# G G#

I suggest you look very heavily into music theory, as one you can understand the alphabet it makes things very easy

I hope that helps, it might look mighty confusing....

hey wantyoplay if u are teaching yourself to play u need to also practice scales to help finger strenth and quickness and speed.

ApeDoctor brought this up-chords change as you move them, because the notes that make them up are changing.  However there's more than one way to finger a certain chord-take C, for example.  You can finger C x32010 (you don't play the bottom string because the "3" on the A string is a C-note, the bottom note of the chord), or you can finger a B (which is quite difficult at first) and take it up one fret-one half step-so it becomes 335553.  Likewise an open G chord, 320003, can be fingered by making an F chord (an E chord up one fret, one half step) and taking it up two frets (two whole steps), so you finger 355433. 
Chords also are changed if you put a capo on the guitar, but all the capo does is the same thing barring that fret would do, but it allows you to finger chords that would be extremely difficult or impossible to finger using barre chords in an easier way.  I hope I didn't confuse you with all this! Happy playing