The major scale is a series of 8 notes in alphabetical order that has the familiar sound:
The G major scale starts and ends on the note G and contains an F sharp (F#) note.
An octave is the range of 8 notes of a major scale. The first note and last note of a major scale always have the same name. In the G major scale the distance from the first G to the G note above it is one octave (8 notes). The following example is one octave of the G major scale. Once you can play it, practice it using eighth notes as well as quarter notes.