A routine is like a habit or sequence that doesn't vary. There are daily routines and dance routines, and maybe even daily dance routines.
Something routine isn't unusual: routine things happen all the time. Most jobs have a routine — things that must be done on a regular basis. People often get surprised by things that aren't part of their routine, or "shake up their routine." Computer routines are predetermined and predictable. Singers and dancers also have routines — the planned performances they've (hopefully) been practicing.