There are several good resources on the Internet for finding Latin root words, prefixes and suffixes, including LearnThat.org and ReadingRockets.org. Both list common Latin root words and their definitions, along with examples of how they are used.
Root words are generally added as a prefix or suffix to an existing word in order to make a new word. For example, the Latin root "ambi," meaning "both," is the basis for ambidextrous and ambiguous. Learning common Latin roots help students and English as a Second Language learners understand the meaning of new words. Knowing Latin roots is especially important for those studying medicine and other hard sciences.