What is a religious sect?

[Justin Wesley]

A sect is a subgroup of a religious, political, or philosophical belief system, usually an offshoot of a larger religious group. Although in past it was mostly used to refer to religious groups, it has since expanded, and in modern culture can refer to any organization that breaks away from a larger one to follow a different set of rules.

https://en.wikipedia.org/wiki/Sect

[Dakota Schaefer]

"The word sect comes from the Latin word secta, which means “school of thought.” It is a subjective term that may apply to a religious faith or denomination, or it may refer to a heretical splinter group."

Source: http://www.gotquestions.org/sect-cult.html