A tidy place is neat and clean, and not at all messy. There's a place for everything, and everything is in its place. Things are put away. Spaces are clear. It's easy to work and play there, and it's easy to find everything you need. Ahhh. Don't you love tidy drawers, tidy workspaces, and tidy rooms? I do!
Of course, after a busy day, you might look untidy, with messy hair, food on your face, and wrinkles on your clothes! Spaces, too, can be untidy if they're a mess, with stuff everywhere. It's hard to work or play in an untidy room.
So when your space is untidy, it's time to tidy up! When you're tidying, or tidying up, you're making your space neat and clean. You're putting things away, clearing off the floors and the counters, making everything orderly and organized.