I ride a 84 team miyata with 28mm gravel king on gravel....so technically that is a gravel bike.

as noted basically it a range of bikes that have clearance for bigger tires and no full suspension

not thing is hard and fast

most would be a ton faster than a mountain bike on the roads, and trails they are intended for

some can do bike packing, some are all speed

closer to a road bike than a mountain bike

at this point mix of marketing, current cool thing and practical capability.....