A DC motor mostly consists of coils and gears. But to understand what really is a DC motor and how it works, we need to look inside of it and understand the physics behind it. Two magnets with opposite polarity are attracted to each other but with the same polarity they oppose each other. There are various DC motors on the market, but to understand the idea behind magical torque produced we will go through a simple DC motor, like the motor we will use later on. The following image shows a simple DC motor, taken apart:

On the left-side of the image, we can see the outer part of the motor where there are two magnets with different polarity. On the right-side of the image, we can see the shaft, wrapped with coil. Applying voltage to the coil, makes it act like a small magnet. This coil-created magnet opposes or attracts the fixed magnet on the outer part. As a result, we have the final rotation of the shaft. We usually add some kind of gears or similar components to the shaft and control the exact rounds per minute (RPM) that we want.

The more current the coil has as input, the stronger the coil-magnet is. The stronger the coil-magnet is, the more RPM the shaft has.