These cars have been written off by an insurer in the past due to damage, then repaired and put back on the road. A listing on Browse Cars means the seller is representing the car as repaired and roadworthy.

Cat S — structural damage, professionally repaired.
Cat N — no structural damage; usually cosmetic, or not worth repairing at the time.
Cat X — previously reported stolen, then recovered.

Tip: ask the seller about the repair history, and for an engineer's report if they have one.