Don't listen to Yo_John, that is NOT how the Chalice dungeons work.
Yes there ARE random ones, you can make random chalice dungeons, but there's an entire 'linear' progression of pre-made ones, too. Basically, each chalice dungeon has 2-5 pre-made 'levels', each one consisting of a maze-like level design with treasures and a switch to unlock the door to a boss. It's like if you were playing a platformer, each chalice is a world consisting of a series of levels, each level with a boss. It's...kind of its own thing.
there's like 4 different types of chalice, each type has like 3-5 different chalices, each chalice has 2-5 stages, each with its own boss. You could, in theory, completely ignore the entire main game and get lost in 50 hours of Chalice Dungeon Crawling. No joke.
Yes, don't listen to me...my only statement was that from what I heard, it seems like a pretty cool concept lol.