To answer your question, the Ford website would provide the best actual "definitions" of the various options.
That said, most of them should be obvious, especially if you play around with the configuration tool a bit.
Right off the bat, you should notice that the wheelbase is not selectable for a pickup truck. It is tied to your choice of cab and bed length. File it under "Nice to know."
Cab style should be a no-brainer. If you don't know the difference between a standard cab, extended cab (aka Supercab), and crew cab (aka SuperCrew), a standard cab has one bench seat for up to 3 people, a SuperCab has a second row of seating for short/small people for up to 6 people, and a SuperCrew has a larger second row of seating for normal size people.
Bed length depends on whether you want to haul 6.5' long stuff or 8' long stuff. Truck campers are classified as "short" (6.5') or "long" (8') bed campers. There are many more long bed than short bed. Short bed will limit you on what campers you can choose from, but a long bed crew cab truck is a serious boat to maneuver in parking lots, so you have to take that into consideration.