APA Style is created by the American Psychological Association (APA) and is used in many different fields including the social and behavioral sciences, health care sciences and natural sciences.
There are several editions of the APA Style where the seventh edition (APA 7) is the latest.
APA Style uses the author–date citation system with a brief in-text citation corresponding to a full reference list entry. The in-text citations include author and date of publication of the cited work, within parenthesis. If the author is already mentioned in the text you only need to include the date in the parenthesis. Each cited work must appear in the alphabetical reference list at the end of the text. Each work in the reference list must be cited in the text. Note that both paraphrases and quotations require citations. See how you write in-text citations and reference list entries for different type of works under examples in the left-hand menu.
Read more about APA 7 in the American Psychological Association's APA Style and Grammar Guidelines.