Why do you ask? What does it matter what's between those two garage doors?

It could be anything. It could be garage space to store "toys" and tools. Maybe it is their mudroom area with a powder room. Maybe it is their laundry area. Maybe it is a big pantry area. Maybe a home gym area. Maybe a dog room, etc. etc. etc.

Looks like the single car garage was a later addition to the main house, with a 2-car garage.

Peek in the window to find out.

Around where I live those setups may, yes, be a workshop/business run out of a garage or...as @kootenaycapable suggested, a separate garage door and entrance to a separate rental suite/apartment.

Actually...I hung around until late afternoon when they raised the center portion between the two doors for this:

Yeah, I think the one in the rear is for a golf cart. Perhaps there used to be a porch back there, then the homeowner decided to enclose it for their golf cart.

I have a three-car garage (three doors side-by-side) and golf carts are in 2 of the bays. And my car is in the other. :)

The split garage, one car on one side and two car on the other side, is a common treatment in some of our neighborhoods. The single car garage may or may not be a golf cart garage. The split design is intentional rather than an add on.