When a song consists of notes from a particular scale, it is said to be written in the key which has the same notes as that scale. For example, if a song contains mostly notes from the C major scale, it is said to be in the key of C major. The songs you have played in this book that start with a C chord written above the first bar of music are in the key of C major.
Morning Has Broken is a well known folk song. It is written here in the key of C major.
Within a key, certain chords are more common than others. After a while you will become familiar with the chords that belong to each key. Certain keys are easier for guitarists to play in than others, therefore you should learn how to transpose (change the key of a song) so you can change a song that is in a difficult key (one that contains lots of sharps and flats or difficult chord shapes) into an easier key.
The most common chords in the key of C major are:
For more information on transposing and chords, see Progressive Guitar Method: Rhythm.
As well as the standard acoustic guitar, there is another version called a Cutaway where part of the body of the guitar is cut back and reshaped along the side of the fretboard. This makes it easier to play notes high up on the fretboard, which is great for playing lead solos on an acoustic guitar. Many players who frequently switch between acoustic and electric guitars prefer to use an acoustic cutaway .