A credible source is a source that readers can trust. The authors ideas should be his or her own and should be backed up by evidence and proper citations. The source also gives both sides to an opinion.

A un-credible source is a source that does not have ideas that people can trust. The ideas and topics discussed are not reliable or credited by the author. They are also not backed up by facts. These sources can easily be editied by anyone.

An attractive source is one that people choose based on the looks of the source, where it came from, or the similarity to other things.

I think that the attractiveness of a source matters. People are more willing to trust a more well named brand of information like the Washington Post or a database from a college library than they are willing to trust a random website or wikipedia.