With drop handlebars, fat, knobby tyres and disc brakes, a gravel/adventure bike combines the speed of a road bike with the versatility of a cross-country mountain bike, so you can explore dirt roads and trails on a bike that still works well on Tarmac.
These bikes are the ultimate do-everything road bike. They usually have mountings and space for mudguards and racks, so you can use them for road touring and commuting as well as their main job of riding dirt.
Gravel/adventure bikes are similar to cyclo-cross bikes, but usually have steadier handling for all-day riding and a wider gear range. Nevertheless, if you fancy a go at racing cyclo-cross, a gravel/adventure bike will get you started.