Different microphones have different ways of converting sound. The two most common types of microphones are dynamic microphones and condenser microphones. The components within a microphone depend on the purpose the microphone was meant to serve and the technical way the device converts electricity.
The diaphragm is the one thing all microphones have in common, regardless of how the microphone converts energy. The diaphragm is a thin piece of metal, plastic or aluminum that vibrates when it is struck by sound waves. The diaphragm is located in different places on different types of microphones, but on a regular hand-held microphone it is located in the head. The diaphragm is crucial to the function of microphones because when it vibrates it causes other pieces of the microphone to vibrate and function.
The coil is a component of dynamic microphones, which are general multi-purpose microphones. The diaphragm is attached to the coil, and when the diaphragm picks up vibrations the coil also vibrates. The coil will move against a magnet, generating a current within the coil that is channeled by the wires.
Capacitor plates can be found inside condenser microphones. Essentially, capacitor plates are two metal plates with a voltage between them. One of the plates in a condenser microphone is made of really light material and works as a diaphragm would -- picking up sound waves. When the thin plate is struck, the distance between the two plates changes and a charge occurs. For a capacitor to work, the microphone must have a battery.