What does the name SNAPSHOT in jar mean? / What’s wrong with *snapshot*.jars?

I am using bitlyj snapshot jar to shorten URLs from the following link.

http://code.google.com/p/bitlyj/downloads/list

Will somebody explain me the term snapshot.jar? Are snapshot.jar files unstable or is there anything wrong with these kind of jars? What does ‘snapshot’ generally mean?

Answer

Yes, those files are usually automatically created from the current development branch without any manual testing.