Terminal to terminal
Terminal-to-terminal means you take the car to a storage lot and collect it from a lot at the other end. The truck does the highway miles. You do the drives on both ends. That is not door-to-door.
Terminal-to-terminal shipping puts the car on a lot the carrier or its agent controls. You drive there, or you pay someone to. At the destination you collect the car from another lot. The car may sit before it loads and after it unloads. Ask who has the keys during those days, and whether storage after a certain day costs extra.
Why the quote can be lower
You are doing the city miles the big truck would otherwise attempt. A terminal quote and a door-to-door quote are two products. Put them side by side for the same car and the same dates. Do not assume the cheaper line includes a driveway pickup. Read the line that names the lots.
How it differs from door-to-door
Door-to-door brings the truck as close as the law and the street allow. Terminal-to-terminal makes you the first and last driver. Neither phrase promises a pickup at a set hour. You still need a bill of lading, a condition note, and the carrier's docket. RideShipper does not run the lots.