A wheel is a circular device that is capable of rotating on an axle through its center, facilitating movement or transportation while supporting a load (mass), or performing labor in machines. Motorcycle wheels come in three basic varieties: pressed steel, spoke and "mag" casting. Pressed steel wheels are found almost exclusively on cheaper, lower performance machines such as entry level standards and scooters. Everybody knows about spoke wheels—they're found on bicycles. The spoked wheels designed for motorcycles are larger, stronger and more expensive. There is some variety in design of spoke wheels. The major design variables are the shape and material of the rim and the pattern of the spokes that hold the rim to the hub.
Increasingly, the trend in motorcycle wheels is to mag wheels. Mag wheels are generally lighter, stronger and more likely to stay "true" (i.e., round and straight) than spoke wheels. Mags require less maintenance and inspection. Wheels size plays a significant role in bike performance. Larger diameter wheels are more stable, but they require more effort to turn. Smaller wheels are more responsive, but are not as stable. This is why cruisers have large diameter wheels and sport bikes have small diameter wheels
Commonly, rims are made of steel, and usually this works fine. If one has some real performance considerations, one may want rims made of alloys such as aluminum, titanium or another stronger and lighter material. Alloy rims are found on off-road bikes and high performance machines on which the wheels are going to take a real beating. Rim maintenance involves a periodic check to determine that they are true and round, and firmly affixed to the hub by the spokes.
Spokes come in a number of sizes or gauges, and are laced between the hub and the rim in a variety of patterns. The engineers who designed your machine know more about spokes and rims than you do, and settled on a spoke gauge and lacing pattern to match the motorcycle's intended purpose. Size or lacing pattern knowledge is not required unless you are planning serious riding.