You don't get the number of gears inside a hub as an external derailleur may provide, although 7 and 8-speed hubs are now available that can deliver virtually the same overall range – and range is what really matters.
Other practical features may include integral lighting, a chaincase or at least a partial chain cover, plus a propstand and a built-in lock, all of which make this kind of bike most convenient to use. Simply jump on and ride is exactly what you want for everyday transport.
The handlebar grips will be angled from the near-straight mountain bike bar, so your wrists adopt a more relaxed alignment - like the 'quarter to three' or 'ten to two' we are told to use on a car steering wheel - or a multi-position 'butterfly' bar may be fitted. See trekking bikes for more about that.
If anything, the riding position will be a bit more upright than a trekking bike or hybrid, upon the assumption that you don't want to pedal too hard and get sweaty on your way to work or the shops. That makes sense and generally holds true – it’s how the overwhelming majority ride in countries where everyone cycles. If, as a cycling enthusiast, you want all those practical city bike features on something lighter and/or with a more athletic riding position, you’ll have to modify the riding position or customise some other kind of bike.
Despite the name, city bikes are just as good for transport in the countryside and leisure rides – all the same things as a trekking bike really. They’re just a bit heavier, marginally less efficient and seldom have such a low bottom gear. So the trekking bike, hybrid or especially the touring bike, has a more rewarding performance and copes better with steep hills.