Citation templates provide a uniform, easy way to cite sources. The inclusion of a template here does not necessarily mean that the sources in question are appropriate references; for details, see Wikipedia:Reliable sources and the individual template pages.
Some templates may be marked FOR TESTING ONLY. Do not use these in articles, if requested on the template page itself. Take a look at the template page before using it.
Note that the use of citation templates is not required. The information can be just as easily written out without the use of a template.