What is an online data base ?

I am doing a research paper and have to do works cited in MLA format, http://www.nimh.nih.gov/health/publications/social-phobia-social-anxiety-disorder-always-embarred/social-phobia-social-anxiety-disorder-always-embarred.shtml is this considered an online data base? if not, what would it be considered and how do i format it for MLA style works cited, Thanks!