The G chord on the guitar is usually one of the first chords new players learn. It sounds great, it's easy to play, what's not to like?
Here is the G chord on guitar in open position. It is played by placing your first finger on the 5th string 2nd fret, 2nd finger on the 6th string 3rd fret, and 3rd finger on the 1st string 3rd fret. The other strings are played open. As a complete beginner, this chord shape will feel foreign and difficult. As your muscle memory forms, this chord will be as routine as ever. Don't give up, it gets easier.
Another common variation of the G chord is this barred version played on the 3rd fret. It uses the E chord shape. To play this chord, you bar all strings with your 1st finger. You then place your 3rd finger on the 5th string 5th fret. Then place your 4th finger on the 4th string 5th fret. Lastly, place your 2nd finger on the 3rd string 4th fret. This one takes some getting used to, but as you build your hand strength it will become easy.
This variation of the G chord looks just like the F chord, but is played on the 3rd fret. As you learn these chords, you will notice a lot of patterns. This is one of them. Use this version to leave off the bass notes and have a more higher ranged sound.
If you want to look real fancy, play this version of the G chord on the 10th fret. This is a bar chord of the A shape. To play it, you bar across the 1st through 5th strings with your first finger at the 10th fret, then bar the 2nd, 3rd, and 4th strings with your 3rd finger at the 12th fret. Notice the different voicing of this version. It really has a different sound than the first version I showed.