What do the following extensions mean?

.com= .company
E.G.= wikipedia.org, wordpress.org, craiglist.org

.gov=.government
E.G.= irs.gov, nasa.gov, nih.gov

.net=.network
E.G.= slideshare.net, secureserver.net, sourceforge.net

.sch=.school

.ac=.academy
E.G.= digitaluniversity.ac, say.ac, dictionary.ac

.co=.company


.ed=.education

.org=.organisation