these are some things that a medieval castle has
Arrow Loops - These were slots in the walls and structures that were used to shoot arrows through. They came in a wide variety of shapes and sizes.
Ashlar - Blocks of smooth square stone. They can be of any kind of stone. It is the technique of closely joining them together. A good example of Ashlar can be seen in Bodiam castle.
Bailey: This is a courtyard or open space surrounded by walls.The walls that make up the Bailey are also considered to be part of the Bailey. A castle could have several. Sometimes they were called the upper bailey and lower bailey or the west bailey and east bailey.
Barbican: A stone structure that protected the gate of a castle. Think of it as a gatehouse. It usually had a small tower on each side of the gate where guards could stand watch.
Barmkin: A yard surrounded by a defensive wall
Bartizan: A small turret at the corner of a tower or wall. It is usually at the top but not always.
Bastion: A tower or turret projecting from a wall or at the junction of two walls
