A backer rod and some repair caulk are great for minor fixes
The crack repair will depend upon what the cracks are, how bad and what caused them.
KMS explains the method of correcting the spaces between each slab which are control cracks placed in the driveway to prevent larger and uneven ones from developing.
If the cracks are small and not displaced, one side being higher then the other, a good quality caulk that blends with the cement can be used if the cracks are cleaned out, dry and not crumbling. If the cracks are larger then clean out, prime using cement primer found in cement isle in box stores, Then using hydraulic expanding patching compound that will seal the cracks tight.
The big trick regardless of the crack is to be sure its clean, debris free and dry.
I would just fll in the gaps wth ready made cement-and trowel it off ..that's what we did for that same problem in the garage worked like a charm
Used to be that you had to clean the concrete with muriatic acid then fill the crack with new cement. But right now there are some great products out made just for patching cracks in concrete. You should go wander Home Depot and Lowes and ask a lot of questions.