Originally Posted by Spartacus

Yeah...

A regiment is kind of the parent unit of a battalion. Its like you sharing your last name with your parents, you are part of the family but are an individual. There can be multiple battalions, or just one.

A collection of battalions from multiple regiments can be organized into a brigade. The reason for this is to create flexibility and promote mobilization, as well as create a more self-sufficient combat ready team.

An example of this is the 25th ID 4th BDE CT. It is comprised of:
2 Airborne Infantry Battalions
1 Cavalry Battalion
1 Field Artillery Battalion
1 Special Troops Battalion
1 Support Battalion

Note that every unit comes from a different parent regiment.

Hope it helps!