Learning guitar these days pretty much always involves reading tab.  If you are just starting and don't know what tab is, it's simple:  It's a 6 lines, and each line represents a guitar string.  The numbers written on the line indicates playing that fret, on that string.  The bottom line is the low E string, the top line is the high E string.  Here's an A minor bar chord:
----5----
----5----
----5----
----7----
----7----
----5----

The internet offers a huge repository of tabs, for pretty much any song you can imagine.  In my teaching, I provide tabs of whatever we are studying.

There is something to be said for traditional music notation.  It is a denser, more information-rich means of conveying musical data.  Each note can display its pitch, its duration, and its relation to the notes around it-- it is very difficult to perceive intervals from guitar tab, but it can become second nature to perceive intervals in traditional notation. 

Sght reading music is itself a discipline, and I only teach it when the student feels the need.  Of course, I encourage it.  But, tab is more expedient in terms of showing guitar riffs and licks, and you use your ear to determine the rhythmic intricacies. 

A great program to get is Guitar Pro.  It is the standard for getting tab on the computer.
 
There are many websites that offer lot's of tabs.  Here's a nice one:  G Tabs
The Guitar Pro website has a page listing many more of these tab sites.