A sect is typically a smaller religious group that has broken away from a larger religion, often due to disagreements on philosophy or theology, and formed its own set of beliefs based on these points of contention. For example, Sunnis and Shias within the Islamic faith are both considered sects, since they adhere to many of the same Islamic beliefs but differ in how they interpret religious teachings.
The word "sect" is derived from a Latin word meaning "school of thought" and is used to denote different branches within belief systems. Many of the world's religions contain a number of sects, and while some are considered heretical by the larger branches of those religions, many are widely accepted. In Judaism, Orthodox and Hasidic Jews are separate sects within the same religion, sharing common beliefs and practices drawn from the Old Testament but disagreeing on how those practices should be implemented and maintained.
Christianity has a number of sects as well. Early Protestant churches were considered sects, and the modern Protestant belief system has many branches and practices that share overlapping ideas. While Baptists and Lutherans practice their religion differently, they have significant beliefs in common that stem from the Christian belief in Jesus as a savior.
The word "sect" can also be used within secular groups, although this is less common.