Transit VLANs

I can seem to get a clear answer from google searches on this topic, I'm trying to find out the purpose of a transit or "stub" VLAN. I've set them up before, my own home network uses a transit vlan between the core switch and the firewall but now i'm having to set up several of our location with transit vlans. Just to be clear because I've heard it called multiple things, instead of the firewall and switchport being on the same network as the internal host it's on it's own separate vlan/network.
What exactly are the benefits of that configuration? I've seen security mentioned, some people say filtering, etc but I can seem to get a clear answer.