Chapters

This is my question of the moment. What's a chapter? No, seriously, what is it? I know there are lots of rules for a story arc, and a character arc, and all that, but what makes a good chapter? Should it rise and fall like a story does? I mean, does it have a beginning, middle and end, just like the story does? Should a good chapter be complete in and of itself? I know lots of people write cliffhanger chapters, is that wise? Should each chapter be roughly the same length as the one before and after it?

Does anyone have any good rules for subdividing a large piece of writing? Say, novel-length? Is it best to just write it and let the chapters form themselves?

Hypothetically speaking, of course. Should anyone happen take up writing again.