well I would suggest they did their own research , but to be honest I can't imagine there's anyone on here who doesn't know ?? as we are all ancient .
do you not know or are you asking on behave of someone who may not know?
anyway I googled it and this is what it says .
A Cat N motorcycle is a motorcycle that has sustained minor damage and can be repaired. The damage is typically cosmetic, such as damage to the steering lock or fairings.