Citation managers allow you to collect and organize citations and then generate bibliographies.
Citation generators are tools in which you type the information regarding the citation (instead of pulling directly from a database or catalog) - they usually have a form to help guide you in what information is needed - and then they format it into the style you need.
Ask your instructor for his or her citation preference as each may have a particular style they wish you to use.
The Internet guides are helpful but they are an abbreviated version of the printed manuals. Come into the library for any citation that the internet guide does not address.