Ionian is the correct name for what is more commonly called the major scale.

A pentatonic scale is made up of five notes. A major pentatonic scale consists of the root, 2nd, 3rd, 5th & 6th scale degrees of the major or Ionian scale before repeating. A minor pentatonic consists of the root, 3rd, 4th, 5th & 7th degrees of the natural minor scale.

Scale and scale modes is a pretty big area of study, but there are plenty of music theory lessons on here.