Sorry for a strange and/or misleading title...but could someone please explain how generations work?

For example...The Baby Boomer Generation lasted for several years and the people born in that generation are noted as Baby Boomers...Duh...lol but my question is...how is a generation determined? Does it go by years? Or a certain event? What even is the new generation...? I'm 19 so would I be a part of the new generation or is there a generation that has been made before mine? I'm soooo confused...please help...
Probably by decades.

I see it musically though. My dad was born to The Beatles era and I was born to the Nirvana era. Unfortunately.
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I find this funny for some reason

Same. It's kind of like a couple drunk guys sitting around trying to solve a simple problem. The best of times.
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... isn't mung like, a bean?