I notice that the term sect is more often applied to non-Christian religions by the media. This is a lovely sort of wordcraft that helps put a negative spin on the word.

In answer to the question, sects are usually groups that share the same religion, but have significant differences in their worship styles that differentiate them from other groups. For example, in Islam you have various sects that are both Muslim, but fundamentally different, i.e. Shiite Muslims vs. Sikh Muslims.