I'm an ignoramus on this topic and am still wrapping my head around the differences in the categories of bikes. I grew up with BMX bikes, road bikes, and maybe mountain bikes. I'm riding a Giant hybrid. How does a gravel bike compare to a fitness bike or an endurance bike? They all seem to be road bike-ish but have a more upright position. I suppose the gravel would have the knobbiest/fattest tires of the bunch. What else is different?