Playing for Keeps

Castle: A medieval fortress, built primarily as a military stronghold. Warfare and security first, comfort and nobles' living quarters second.

Palace: A post-medieval aristocrat's home du season. War being primarily a thing for distant battlefields or seas now, the emphasis of this structure is on beauty, elegance, comfort, and showing off how wealthy you are.

Keep: The most important part of the castle. This structure is the first thing to be built and the last thing to fall in the event of an attack. It sits in the middle of the castle grounds, usually on top of a mound of dirt and sometimes surrounded by a moat. In early centuries, keeps were usually round or square; in later centuries, they took on fancy shapes like quatrefoils. Actually, the term "keep" arose in the 16th century. Prior to that, it was called a "donjon."

Motte-and-Bailey: The precursor to castles. The motte is a huge mound of dirt. The bailey, or ward, is the fortified structure on top of the motte. These were originally made out of wood, but got upgraded to stone. Baileys and keeps are like rectangles and squares. A keep is a bailey, but a bailey isn't necessarily a keep. Some (later) castles had multiple baileys, but the main one was the keep.

Curtain Wall: The main wall enclosing the bailey. These could be anywhere from six to 20 feet thick.

Battlements: The walkway on top of the curtain wall, where you could position your archers.

Since Bristol Castle was demolished in the 17th century, I'm going to rely on some old study abroad photos to illustrate.

Palace

Giant driveway, large windows

Castle

Thick barricaded wall to greet you, "windows" reduced to arrow slits

Palace

My ballroom is fancier than your ballroom.

Castle

Um, well, the fireplace is over in the corner...and the tapestries help with the drafts.

Palace

Look at my flower garden!

Castle

Say hello to my catapult.

Palace

No, no, darling--this is the back staircase. The grand staircase can fit three ball gowns across.

Castle

Bahaha. Only one of you can squeeze through at a time. Now I can kill you all single-handedly!

Actually, fun fact: most castle stairways curve to the right, so that a person defending the castle could strike with his sword-hand, while the attacker would be forced to use his left, non-dominant hand. (Of course, this didn't work if you had two lefties going at it.) Also, castle steps were purposely made to be uneven. That way, you couldn't get into a rhythm running up the stairs--invaders would have to walk slowly or risk tripping and falling.