A castle is a fortified residence for a medieval noble. Castles come in all shapes and sizes, but knowing a few general terms will help you understand them.
The Keep (or Donjon): A high, strong stone tower in the center of the castle complex that was the lord's home and refuge of last resort.
Great Hall: The largest room in the castle, serving as throne room, conference center, and dining hall.
The Yard (or Bailey or Ward): An open courtyard inside the castle walls.
Loopholes: Narrow slits in the walls (also called embrasures, arrow slits, or arrow loops) through which soldiers could shoot arrows at the enemy.
Towers: Tall structures serving as lookouts, chapels, living quarters, or the dungeon. Towers could be square or round, with either crenellated tops or conical roofs.
Turret: A small lookout tower projecting up from the top of the wall.
Moat: A ditch encircling the wall, often filled with water.
Wall Walk (or Allure): A pathway atop the wall where guards could patrol and where soldiers stood to fire at the enemy.
Parapet: Outer railing of the wall walk.