A cozy mystery most often takes place in a small town. The small size of the town makes it believable that everyone involved in the mystery would know each other. The amateur detective is a likeable person who is able to get the community members to gossip about each other to help solve the mystery. Often there are one or two characters like this in the book. These characters help fill in the blanks to help the amateur detective solve the case.
The cozy mystery detective is usually not part of the local police department. Sometimes she or he is married to someone who is either part of the police department or the medical examiners office. This gives them an easy in with the police. Usually the police pooh pooh the amatuer until she solves the case for them. So basically it's just a mystery novel set in a cozy little town solved by someone like Jessica Fletcher (Murder She Wrote).

