What Does Generation Mean?

The word generation is used a lot in the bible. It can mean anything from 'millennials' to people born in the late 20s and early 30s. But if it means something different, then we might not be able to put a time line on this whole thing. The question that hangs out there with t word generation being in play is when? And the way to get to the bottom of that is to dig into the different places where this word occurs throughout the text of matthew.