Something that makes experienced cyclists upset is to see someone riding a bike on the road with tires that have large rubber knobs (or “lugs”) on them. Those tires are designed for off-road bikes. They provide good grip in loose conditions and a degree of comfort on a downward ride that can be spine-tingling. On a hard flat street surface, a significant proportion of the biker’s effort goes into overcoming the rolling resistance provided by mountain bike tires.
A rider with a mountain bike with the right kind of wheel rims who intends to ride it off-road should fit it with mountain bike tires, but they should not be used on a bike that is intended for use mainly or exclusively on the road.
At the opposite extreme are “slicks” which are, essentially, bald tires with no tread, and no rolling resistance at all. Some cyclists love slicks and there are excellent examples around, but most cyclists recognise that while slicks are wonderful in dry weather, they are not ideal, and can even be dangerous, for riding on wet roads. All-weather tires is the name given to tires that have better grip and will disperse the water when the road is wet.
Cyclists who race will often use tubular tires. These come as a sealed unit, with the inner tube sewn into the casing. They need rims that are made for them, to which they are taped and glued. The majority of cyclists will use “clincher” tires where the inner tube is completely separate from the casing. In either case, it is a good idea to choose a casing with built-in Kevlar puncture protection.
Tires will usually state the range of pressures to which they should be inflated. It is important to stay within that range; a tire that is underinflated will increase the rolling resistance and is more likely to puncture or, in extreme cases of under inflation, to come off the rim while a tire that is inflated beyond the maximum figure may explode!