The modes of the major scale, sometimes called "church modes," usually referred to as just "modes," are an important musical concept to learn, because they can be building blocks for improvisational ideas and patterns. There are 7 Church Modes.
1 - Ionan
2 - Dorian
3 - Phrygian
4 - Lydian
5 - Mixolydian
6 - Aeolian
7 - Locrian
There are more modes, but many other modes are based on these 7, so it is important to learn them first.