Tab is just a way to illustrate fingerings on a fretted instrument.
You have six lines. Each line represents a string on your guitar.
The sixth string is at the bottom and the first string is on top.
When any string has a zero you play that string open.
The numbers on a string tell you what fret to play.

So in this example you would play your sixth string at the sixth fret, your fifth string at the fifth fret, your fourth string at the fourth fret, your third string at the third fret and so on.

|------------------1-|
|---------------2----|
|------------3-------|
|---------4----------|
|------5-------------|
|---6----------------|