Fast Registration is a way to register someone for a program without having to enter them into CORE first (as a member/non-member). Think of it as a "Checkout as Guest" type of concept similar to what you see when shopping online.
If a program is set up for this option, CORE will only require minimal information for someone to register and CORE will automatically make a temporary non-member unit for the person. The info on the unit may be inaccurate or incomplete.
When a Fast Registration unit is created, the home branch will be set to the branch of the program division they are registering for if the division is only for one branch.
Fast Registration units are also created when an authorized pickup, who is currently not in Core, is added to a members profile. The home branch will be set to the division branch or the home branch of the participant if the division is for more than one branch.