PsycInfo and PsycArticles are two different, but complementary, databases covering the spectrum of topics under the psychology, psychiatry, and counselling & psychotherapy umbrellas.
These databases share a subject heading thesaurus (APA Thesaurus) which is searchable alongside the standard abstract / title search. Using the thesaurus search is most useful when doing advanced searches for postgraduate and above research.
This video is from the database provider EBSCO
This video is one of the tutorials from the APA (American Psychological Association)
Full APA PsycArticles Coverage List
APA PsycInfo Journal Coverage List
APA Search Help & Training Centre