Hybrids will have lighter frames, a lighter front suspension, usually a suspension seatpost, adjustable stems to move the handlebars, and probably the pedals are a bit closer to the ground than on a mountain bike. They still have you sitting upright like a mountain bike but because of the narrower, street tires they will be faster. Some hybrids' frames are just as beefy as mountain bike frames but many are lighter.
The Trek FX bikes and the like have a bit more aggressive geometry than the hybrids, they don't have front suspensions or suspension seatposts. The tires may be narrower and more for pavement and light trails. The gearing on the lower end models is the same as on mtb's and hybrids but the more expensive models use road gearing, which is higher for more speed(but more work getting up hills).
The Pilot is a road frame, road handlebars, road gearing, road tires but the geometry is more 'relaxed', you aren't bent so far over. Plenty fast, light frame, the kind of bike most people on 'race' bikes should've gotten.
At the other end, there are "comfort" bikes that have lower seats so your feet can touch the ground while still sitting. The geometry is upright. Most have front suspensions, adjustable stems for the handlebars, and the handlebars are swept back. Great for leisurely rides down the bike paths, going to the store, just bumming around. Some models have Shimano Nexus gears in the back. These are gears inside the rear hub, 3 or 7 speeds. Made for people that enjoy riding but aren't interested in racing teenagers.
Even more leisure-oriented are the cruisers. Long wheelbase, fat tires, swept-back handlebars, no more than 7 speeds(most are singlespeed).
Note: it's nearly always cheaper to buy good components already on the bike than to upgrade them later. So, if you feel you must have Deore XTR gearing, save up for the bike that carries it. Really, though, everything but bottom basement stuff is good, just heavier and maybe needs more adjusting.
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