Transitions between sections: Particularly in longer works, it may be necessary to include transitional paragraphs that summarize for the reader the information just covered and specify the relevance of this information to the discussion in the following section.
The main difference between wheel and rim is that rim is not the whole wheel but only a part of the wheel. Key parts of the wheel are rim and disc. The hub may be also considered as a part of the wheel. The hub is wheel base with studs on which the wheel is attached to the suspension. The rim is a cylindrical wheel outer edge holding the tire on the wheel. Main function of the rim is supporting and sealing the tire to the wheel.
Nor are they always the best simple machine to use. It all depends on the work you want to do. A wheel and axle is a simple machine where two components rotate together to transfer force from one to the other. Think of your car or bike wheels or even a round doorknob, and you'll get the idea of this machine. When you put a rope or cable around a wheel and axle, you get a pulley.