What's that difference between Hotel, motel, and inn?

Are there price differences or size? How do I know what works best for travel?What's that difference between Hotel, motel, and inn?
Motel is short for motor hotel and they used to be smaller and quickly constructed by freeways for people traveling by car. Of course, some of them are quite nice these days.





As far as I know, ';Inn'; is just used to make the name of the place sound more traditional.