Gravel bikes are probably the most versatile bikes on the market today. They fulfil a number of roles across different disciplines, commuter bikes, off-road gravel bikes and they can even double up as a cyclocross bike for anyone looking to try out cross racing. Their versatility stems from their dual wheel size compatibility which in turn opens up a whole host of available tyre options which can be catered to the chosen style of riding.
In terms of aesthetics a gravel bike will not look too dissimilar to a road racing machine unless you look at them closely. Where they differ markedly is in the tyre clearance, a road bike will normally have a 28mm tyre clearance and possibly up to 32mm with disc brakes. A gravel bike can be expected to have a clearance in the 45mm to 50mm range. This increase in width serves a dual purpose, firstly it improves grip when off-road, secondly a wider tyre is run at a lower pressure which improves comfort and vibration dampening (compliance).
All gravel bikes will be equipped with disc brakes as standard, disc brakes offer by far the best braking performance than any other type of brake. This is much more beneficial when commuting daily in all-weathers or when riding over mixed terrains / surfaces, which you can expect to encounter when riding off-road.