A motte-and-bailey castle is a European fortification with a wooden or stone keep situated on a raised area of ground called a motte, accompanied by a walled courtyard, or bailey, surrounded by a protective ditch and palisade.
A moat is a deep, broad ditch, either dry or filled with water, that is dug and surrounds a castle, fortification, building, or town, historically to provide it with a preliminary line of defence.
Throughout the Middle Ages the courtyard was packed full of buildings providing accommodation for the Lord and his followers. There were also service buildings: a survey carried out in 1337 lists a chapel, stable, gaol, hall and various chambers. To your right was the Great Hall where ceremonies and banquets were held.
moat, a depression surrounding a castle, city wall, or other fortification, usually but not always filled with water. The existence of a moat was a natural result of early methods of fortification by earthworks, for the ditch produced by the removal of earth to form a rampart made a valuable part of the defense system.
Batter (Plinth) The angled lower part of a tower or wall. Missiles dropped from the top of the towers or wall onto the plinth cause them to richochet horizontally into the attackers doing more damage. Plinths also strengthened the bases of the towers or walls and also made it harder to undermine them.
These gaps are termed embrasures, also known as crenels or crenelles, and a wall or building with them is described as crenellated; alternative older terms are castellated and embattled.
A castle town is a settlement built adjacent to or surrounding a castle. Castle towns were common in Medieval Europe. Some examples include small towns like Alnwick and Arundel, which are still dominated by their castles.
The inner bailey or inner ward of a castle is the strongly fortified enclosure at the heart of a medieval castle. It is protected by the outer ward and, sometimes also a Zwinger, moats, a curtain wall and other outworks. Depending on topography it may also be called an upper bailey or upper ward.
In architecture, the talus is a feature of some late medieval castles, especially prevalent in crusader constructions. It consists of a battered (sloping) face at the base of a fortified wall.
The top of the castle walls were the battlements, a protective, tooth shaped parapet often with a wall walk behind it for the soldiers to stand on. The defenders could fire missiles through gaps (crenels). The raised sections between, called merlons, helped to shelter the defenders during an enemy attack.