What's the difference between a freeway and an expressway?

Excuse me, could you please elaborate on the distinction between a freeway and an expressway? I've heard these terms used interchangeably, but I'm curious if there's a specific difference in terms of their design, function, or traffic regulations. Are there any key factors that set them apart, or are they essentially the same type of road with different names? I'd appreciate your insight on this matter.