This is a tire used for long distance touring. Very similar to tires designed for daily commuting, touring bike tires are designed with foremost with durability in mind to provide for long wear and flat avoidance. Touring tires too also must support heavier loads over longer distances but still offer the cyclist a comfortable ride.
Manufacturers of touring tires tout how their tires combine durability with a relatively light weight. Schwalbe, makers of the Marathon Supreme shown above, writes ad copy like this in describing their tire: "An extremely densely woven fabric made from Vectran protects the new top of the line touring tire . . . yet is nearly 50% lighter than any other touring tire."
Touring tires have more tread than the slicks you'll find on a racing bike to help provide better grip, but they're still definitely more smooth than knobby for lessened rolling resistance.
