I know this maybe a stupid question to most, but what is a group build? How exactly does it work? Does everyone build something from the same period or the same model? I'm just not familiar with "Group Builds". I thought it was people who got together and worked on the same exact model together, but I saw people doing the builds live in different places so thats out of the reasoning? Can someone shoot me a definition. Thanks

Basically what they said. It's a support group for a given subject and kinda a "challenge" call out for you to do a specific model/subject in a given time period. Sometimes there's prizes as a reward for completion as well but that's usually out of the norm.
Really, you can eat dinner yourself but sometimes, it's more fun to eat dinner with all your friends right? That's basically it.
Group Builds I've seen have certain rules to it so it also staying in the confines of those rules. There's special Interest Group Build where you build a specifc model (Tamiya's 1/48 Marder II kit only) or a specific subject (P-51 Mustang Build). There's more wider subject like from a certain battle or theatre of war. And there's grander stuff that's suppose to give you a challenge like the up coming Sci-Fi/Fantasy Movie and TV Scene build.
It's a support group with confined guidelines. Some people like to do it, some don't. Thus why I'm a stickler of staying within certain rules.