There are many different planes for many different uses, but all shape a piece of wood to meet desired needs.

Hand planes are shaping tools where a shaped blade (usually straight) is run over a piece of wood to shape it to a desired result (usually flat).

While the most common use is to flatten a piece of wood, there are many other hand planes that put different shapes to the wood, some are rabbet/rebate planes to create a groove on the edge of a board, others are rounded, like the speciality planes for musical instruments and for making spars. There are also numerous other shapes possible; in the past all mouldings were created by planing and there were a correspondingly large number of shaped planes made, called moulding planes.