There are five basic types of intervals which are listed below.
Perfect
Major
Minor
Augmented
Diminished
Perfect intervals are 4ths, 5ths and octaves. If you widen any of these intervals by a semitone they become augmented, and if you narrow them by a semitone they become diminished. Major intervals become minor if narrowed by a semitone and minor intervals become major if widened by a semitone. Examples of intervals which can be major or minor are 2nds, 3rds, 6ths and 7ths. A diminished interval can be created by narrowing a perfect or minor interval by a semitone. An augmented interval can be created by widening a perfect or major interval by a semitone.