Pentatonic scales have five notes, from penta meaning five.

A major pentatonic (A, B, C♯, E, F♯, A)

There is also a minor pentatonic scale

The structure of the major pentatonic scale is root, major second, major third, perfect fifth, major sixth or in guitar talk, root then up 2 frets, 2 frets, 3 frets, 2 frets and 3 frets

Some players may try and tell you that the pentatonic scales are beginner scales, don't listen to them, most memorable riffs and solos have been written in pentatonic scale