A Motte-and-bailey is a kind of castle, or fortification. Many of them were built in the 11th and 12th century around Europe. These structures were made on a hill (that was often artificial). On this hill, a keep of wood or stone was built. This was easy to build, and the materials were readily available and cheap. However, this meant they were easy to burn down. Also wood rots when it gets wet so the structure doesn't often last long and need lots of repairing. They used to be made out of wood but as time went by different types of castles made of stone became more common as they were much stronger. These were surrounded by a ditch and protected with a stone wall. Motte and bailey castles appeared in England after the Norman Conquest of 1066. Motte and bailey castles were a common feature in England by the death of William the Conqueror in 1087. Their construction was the start of what was to become a massive castle building programme in England and Wales. Motte and bailey castles have been around for 8 centuries and are part of today's history.
Sometimes the hill was already there, like in Castelnou
Motte in Saint-Sylvain-d'Anjou
Sometimes castles were built on the site of the motte, like in Gisors