Wow, when I saw the question, I would never expect to have read this answer, hahahahahahaha.
Just to add a little bit of information about this (it's not a complain, I just would like to share it, because I found it interesting):
The word ‘castle’ comes from the Anglo-Norman French word ‘castel‘, which itself derives from the Latin word meaning ‘fort’. A castle is a fortified dwelling. In other words, there are many kinds of fortifications built for defense, but a castle is specifically used as a residence, as well. In medieval times, castles were usually occupied by someone highborn, such as a lord, knight or monarch. (Shown here is Bodium Castle, England.)
The term ‘palace’ comes from Rome’s Palatine Hill, where the rich and famous built their sumptuous homes in Roman times. So when we’re wondering what’s the difference between a castle and a palace, the most important difference is that a palace is not fortified.