There are several different types of microphones. Each of them is best suited to a different musical situation (e.g., live band performance, or recording session). The type most commonly used for live performances is the dynamic microphone.
These microphones contain a diaphragm and a coil which is activated when the voice causes it to vibrate. They are normally uni-directional, or "front sensitive" which means that sounds entering from the sides of the microphone are amplified less than sound entering from the top or front. Because of their resistance to feedback (the piercing sound made when a microphone picks up the sound coming from the speakers and amplifies
Omni-directional microphones receive sound equally from all sides of the microphone. This makes them useful for back-up vocals in situations where two or more singers share one microphone, but they are not recommended for a lead singer in a live band situation.
Before you buy a microphone it is advisable to visit a music store and try some out. The Shure SM58 microphone in the following photo is a typical professional quality uni-directional dynamic microphone and is one of the most common used by bands. There are also other good microphones available of a similar design. If you intend to perform in public regularly, it is worth spending a little extra on a good microphone as it will make you sound better, which will add to your confidence and make you more comfortable with your sound on stage.