In the last lesson we learned where to find single notes on the guitar. When we play three or more notes at the same time we get a chord.
Chords are the foundation of almost every song, they define the harmony, they are essential in comping and in rhythm playing in every style of music and for a beginner they are priceless for strumming along any song: regardless of the complexity of the original arrangement we can always find a simple way to play a song on an acoustic guitar.
Like notes, we can find the same chord in different places on the fretboard and so we get different 'shapes' or positions, some are simple and some are complex.
'Open chords' are shapes that use one or more open ( not fretted ) strings and are played on the first few frets, usually from the first to the third, and they have the advantage of being both simple and rich sounding, ideal for strumming. They are considered beginners' chords but their rich tone makes them an essential weapon in the arsenal of every pro guitarist.
There are three fundamental shapes for open chords: the E shape, the A shape and the D shape (if you don't know how to read a chord diagram click here).

E shape

A shape

D shape

Starting from these basic Major shapes, with just a little finger shuffling, we can play almost any kind of chord (minor, 7th, sus etc.) and we can transpose them using a barre so we can play virtually every chord: we can move an E Major to the 3rd fret with a barre and play a G, for example.

We can play an almost infinite number of open chords on the guitar but many of them are not as flexible as these three shapes. The most common of these chords are the C and G shapes: they have a beautiful and rich sound but we cannot use them to play, for example, minor chords and they're not very useful with a barre either.

C shape

G shape

Now let's find out how minor and 7th chords are derived from the three basic shapes in the next chapter.