I've been thinking about getting a shotgun mic and I found this video.
A shotgun mic is one that is highly directional (meaning it doesn't capture excess noise... at least it shouldn't, if operated correctly).
You see these often being dangled via a boom (long-necked pole) directly over an actor or subject on movie sets. While these microphones are not readily availble for use with consumer camcorders (because they connect using a standard three-pronged XLR connector), they can be connected via the purchase of another XLR camera adapter online.
The reason for the microphone hanging and pointed downward toward the subject is twofold: background noise is canceled out from the sides of the microphone (so anything that is moving around the actors) and the front end is pointed directly at the subject, allowing for higher signal level (clearer audio) and less noise from outside the subject area.
This funny video explains what a Boom Operator does on set. It's hilarious.
https://youtu.be/Rdf1QAnjSfEhttps://youtu.be/Rdf1QAnjSfE
A REALLY great little video explaining audio issues is here: http://vimeo.com/1080128
