Can Someone Help Answer a Few Questions I Have About Castles?

So, I'm currently trying to figure out exactly how castles were designed.

As I'm aware that castles tended to serve multiple purposes, I'll let you know the specifications,

The castle would be a place for politics and serve as the residence for the royal family.

Now here's where I need help.

What would the layout of such a structure be? I've looked up so many blueprints and websites but I can't find something that would actually apply. I need someone that I can actually talk to so that I can express my confusion.

Edit: To clarify, what rooms and different areas/features would go into the castle?