This document summarizes the key parts and types of medieval castles. It describes the motte and bailey castle, which had an elevated motte with a wooden keep and an outer bailey surrounded by a ditch. It then discusses stone keep castles with thick stone walls and towers. Concentric castles had multiple concentric lines of defense with inner and outer curtain walls. Later, castles evolved into palaces as weapons improved, focusing less on defense. The document defines a castle fort as a fortified, walled residence or stronghold occupied by troops, typically surrounded by defensive structures like walls and ditches.