In Lesson 5 the C Major scale was introduced. The G major scale starts and ends on the note G, and contains an F# note instead of an F note. Play the following G major scale and notice that it still has the familiar sound Do Re Mi Fa So La Ti Do.
The key of C major was discussed in the section on Key of C Major. Songs that are in this key utilize notes from the C major scale. Similarly, songs that are in the key of G major are said to utilize notes from the G major scale. Songs in the key of G will contain F# notes.