APA - American Psychological Association referencing style is a system of in-text citations and a reference list.

In-text citations:

• (Author Surname, Year of Publications) when referring to a whole work   OR
• (Author Surname, Year of Publication, page number) when quoting of referring to a specific page or page range.

Where the Author's name is mentioned within your text, there's no need to include this within the in-text citation.

Examples:

Developmental psychology can be defined as the study of psychological changes in humans over their lifetime (Boslaugh, 2011, p.1).

OR

Boslaugh (2011) defines developmental psychology as "the study of psychological changes that occur in human beings over the course of their lives" (p.1).

Reference list:

• Comes at the end of your document (on a new page);
• Lists all the sources you have cited;
• Is alphabetically arranged by surname of the first author/editor;
• Contains full details of the sources you have cited - these vary depending on the type of publication, see the dropdown menu in the APA 7th edition tab to view examples.
• Is double-line spaced.
• Uses hanging indents of 0.5 inch, where a reference is more than one line long.