Gatehouse
A castle was a huge building or two towers that were connected. It is a type of fortified structure build in Europe and the Middle East during Middle ages.
A barbacan is an archaic term for a barbican, a tower at the entrance to a castle or fortified town, or a fortress at the end of a bridge.
The likely word is castle, a large fortified structure dating from medieval times.
The Gate House controls the entrance through the wall and into the castle. The castle is the name for the entire fortified building. The gate house, keep, chapel, wall (etc) are different parts of the castle.
The site of Edinburgh castle has been fortified since the Bronze age with a seried of increasingly complex fortifications. the current castle structure was built in the 12th century
The Castle in the Forest was created in 2007.
The gatehouse is the structure that defends the main gate, so the gatehouse is always at the entrance.
A portcullis is gate that drops in front of a Castle door. A drawbridge is a moveable structure that allows access across a moat to the Castle door.
A castle that has defense and can be protected from attack.
The barbican was an exterior castle defence situated at the entrance of the castle. The Barbican or 'death trap' was developed as another way to strengthen the main entrance, by adding more defenses in front of it - the barbican confined the enemy in a narrow passage - an easy target for castle defenders! The most common barbican design was a walled passage projecting from the front of the gatehouse.
The outer wall of a castle is a defensive structure that surrounds the castle complex, providing protection against enemy attacks. It is typically made of stone or fortified with towers and battlements to prevent breaches. The outer wall often includes a gatehouse for controlled access and may be further reinforced with a moat or other defensive features.
Castles and palaces are not the same thing, A castle is built as a fortified structure to withstand enemy attacks. A palace is built as a place of luxury.