Difference of beating pattern of flagellum and cilia. Flagellum is the one on the left, cilia are on the right.

A flagellum (plural: flagella) is a long, whip-like structure that helps some single celled organisms move. It is composed of microtubules. They help propel cells and organisms in a whip-like motion. The flagellum of eukaryotes usually moves with an “S” motion, and is surrounded by cell membrane.