What is the difference between a castle and a palace?
When originally built, castles are primarily fortifications. Decor is often a secondary consideration, especially on frontiers. Palaces are more often built with decor and comfort in mind, and far less attention to defense. Certainly, over time, in a settled realm, castles can evolve into grand residences. Also a castle was mainly built to defend and a palace was just for a beautiful place to live.