Todd’s info is pretty much spot on.
Generally, almost every manufacturer makes a karting-specific helmet, and it’s almost always based on their SA-rated helmet, often using the exact same shell. The main difference is the Nomex interior. For example, the Arai SK-6 is the exact same shell as all their GP helmets, just has different interior fabric. The SK also has different a ventilation configuration to get more air in at the lower speeds you see in karting.
Some helmets are balanced a little differently as well for how the helmet will be worn. For example, a motorcycle helmet will sit a little differently on your head, as it’s intended to be ridden with the rider leaning forward and looking up. A karting/auto helmet will sit tilted down more, as more drivers will be sitting upright and back, looking forward.
I always prefer karting/auto helmets for karting, but plenty of people use moto helmets as well and love them equally. The main thing is making sure you’re buying a safe, proven helmet, regardless of it’s original intended use.