Halachah is traditional, Jewish law. It covers a wide range of things -- from when to say which blessing to how to get a divorce. The term itself is singular, so it can be used to refer to a single law or to the body of law. Halachot is the plural, if you wish to explicitly refer to multiple laws. Halachic is the adjective.
- A Glossary of Basic Jewish Terms and Concepts - D through I on Judaism 101
- Information on a class, Halacha Overview, on Torah.org
- Wikipedia's article on Halakha
- Related Chabad.org links on Halachah