Rims can vary in their width, their profile and weight. This would affect the size of tyre, the aerodynamic and ride quality, acceleration and how long the braking surface lasts before it wears out.
Spokes are available in a variety of wire guages. Thicker ones are stronger and heavier. Butted ones are thicker at highly stressed points, and thinner where more elastic characteristics are needed, so are much stronger. Exotic materials are used on up-market spokes, but stainless steel is fine.
The hubs can vary in the precision of their bearings, the effectiveness of dirt seals, and the amount of lightweight material vs steel.

In practice the most important factor in a wheel is the quality of the build, esp how the spokes are evenly tensioned.
Most shop bikes come with machine-built wheels. They are of adaquate build quality, but can often be improved in the hands of a good wheel-builder.