To do something repeatedly means to do it over and over again. If you text your friend repeatedly during her geometry test, she'll probably get annoyed and turn her phone off.
If a teacher tells a student, "I've told you repeatedly that you need to raise your hand before you speak," it means that the teacher has said this many times. This adverb implies an ongoing or even constant kind of activity. At the heart of repeatedly is the verb repeat, which has the Latin root repetere, "do or say again," or "attack again."