Almost as light and fast as a road bike. But a bit more upright riding so it's more comfortable. Wider and more treaded tires means tram lines, pot holes, curbs etc. are less of a problem and can handle rough surfaces and not just asphalt. Mounting points and wider forks allow for mudguards / fenders so rain is no problem. The wider space allows for studded tires during winter. Also easier to mount panniers / luggage carriers to carry stuff home from the stores.
While I love my road bike for long rides on the weekend, I use my gravel bike daily. And it also allows me to go places I cannot go with the road bike, without having to go all mountain-bikey.
Btw, for road biking we often compare aerodynamics using "wattage per dollar". It can be surprising what then should be the first things to improve.