An egress window is a window that can serve as an emergency exit from a living space underground. Do you need one in your basement?
It depends. There are several building codes that cover not only the necessity of the window but also the specific structural requirements of the unit itself. The main factor that determines whether you need an egress window is if you include a bedroom in your basement. Essentially, any room that is at least the size of a bedroom and has a closet would be classified as a bedroom and therefore require an egress window. You can read more about egress windows here.