Now we are on the 3rd string, the G string. As we've already learned, the note that sounds when we play the G string open (at the "zero fret") is called G. If we hold down the G string at the 2nd fret, we make the amount of string allowed to ring a little bit shorter and thus a little bit higher in pitch. It is now called the note A. If we hold down the G string at the 4th fret, we make the amount of string allowed to ring a bit shorter again and thus a bit higher in pitch. It is now called the note B.

With the 4th fret note B we again arrive at that important concept of the same note in more than one place on the guitar.

The note B that sounds at the 4th fret of the G string is the exact same note B that sounds at the open B string (the "zero fret"). This is why we tune the B string using the 4th fret of the G string.

So now we know how to play 3 notes on the G string.

zero fret - G

2nd fret - A

4th fret - B

You can keep going up the string holding down higher frets, playing higher sounding notes. For now we'll stop at the 4th fret. We'll get to those higher notes later. You may have noticed that we skipped the 1st and 3rd frets again. We'll get to those later, too. For now, let's move on to the next string.