The average home camcorder owner will probably think that the on board microphone is good enough, but using an attachable microphone is often what separates professional filmmakers from those that simply film their family on spring break. When people actually get into the professional sound equipment they are usually confused as how to differentiate between the different types. In most audio as it associates with digital video production you are going to run in to dynamic, condenser, and velocity microphones. These are all useful microphone choices, but there are a few key differences that will let you know what you need and when.
If you are looking for durability you will probably choose a dynamic microphone. The dynamic microphone is usually used when you need to reduce sensitivity, such as outside during offensive weather situations that affect the audio conditions. Over all the dynamic microphone can really maintain the sound even when there is a higher sound pressure level. For a higher level of decibels the dynamic microphone will be able to transmit sound without much loss. The dynamic microphone is not, however, known for its sensitivity. If you need to pick up on quiet sounds you are not going to be able to rely on the dynamic microphone. There are a two main types of dynamic microphones, which breaks down to a ribbon and a moving coil dynamic microphone. This can be used for a boom microphone.
A condenser microphone is great for picking up frequency. The condenser microphone is also called a capacitor microphone because it contains an electrical component that has two electrode plates that store electronic charges. The condenser microphone uses phantom voltage and usually takes a power of 48 volts that comes down the cable. You are going to find that the condenser microphone brings in the sensitivity that the dynamic microphone misses. The condenser microphone will pick up the subtleties in sound that may come up, so if you need to pick up the minutia that is around. You cannot rely on the condenser microphone to be durable in most situations, especially in terms of the physical conditions that the microphone is in. Any type of water is going to be a major interference with the condenser microphone.
The velocity microphone is not in the same parallel as between the condenser microphone and the dynamic microphone. The velocity microphone is actually a much older design than the dynamic or condenser microphone, and does not get as much use anymore. The velocity microphone achieves its sound by suspending a diaphragm in a magnetic field. The velocity, or ribbon, microphone is often used to record instruments or voice narration. Do not expect to find velocity microphones on most film or audio engineering environments, but you may find them in older recording studios.