I have heard different things regarding the requirements for counting a
bedroom as a bedroom.

Mostly I have heard that it must have a closet and a window.

But I have also heard variations on that for rooms that are below
grade.

Some say they must have a window that of a specific type that will
allow a person to crawl out in the event of a fire.

Some say that they must NOT be 100% below grade, that if they are 50%
below grade then they are ok.

What are the rules?
Is it specific to your town?