Shown below are some of the fundamental chords used when playing guitar:
(The yellow box marker shows the most important note in the open E chord)
It is important to note where the root is for each. For the G chord, the root is on the 1st, 3rd, and 6th string. For the C chord, the root is on the 2nd and 5th string. For the D chord, the root is on the 4th string. For the A chord, the root is on the 3rd and 5th string. For the E chord, the root is on the 1st, 4th, and 6th string. Memorizing all of this allows for greater freedom in playing, as will be shown later. Memorization is not essential to getting a great sound out of your guitar though!
An alternative to guitar tabulature, is guitar chord charts. This page describes how to read chord charts.