APA Style is published by the American Psychological Association (APA).
The American Psychological Association states that the style guidelines were developed "to advance scholarship by setting sound and rigorous standards for scientific communication. They sought to establish a simple set of procedures, or style rules, that would codify the many components of scientific writing to increase the ease of reading comprehension" (Publication Manual of the American Psychological Association, 2010).
In-text citations are citations that appear in the text of your essay and refer to a specific idea, quote, or page. APA uses parenthetical citations -- this means APA in-text citations put the relevant citation information in parentheses before the end of the sentence but before the period (i.e. like this).
For APA style, if you are referring to an idea from another work but NOT directly quoting the material, you only have to make reference to the author and year of publication and not the page number in your in-text reference.
If, however, you are directly quoting the material, you will need to reference the author, the publication year, and the page number in your in-text reference. Singular pages should be indicated by p. and multiple pages should be indicated by pp.
Bibliographic citations appear at the end of an essay -- APA style calls this the Reference List and should be formatted as its own separate page at the of the essay simply titled, References. Bibliography entries should all contain these basic elements:
Reference Lists should also follow specific formatting requirements. References should be: double spaced; use the hanging indent (the first line is not indented but the following lines are); authors' names should be listed by last name, and authors' first and middle names should be written as initials. Here are examples for a book and an article citation:
Freud, S. (1899). The Interpretation of dreams: The Complete and definitive
text. Franz Deuticke, Leipzig & Vienna.
Surbeck, K. (2018). Sigmund Freud—early network theories of the brain. Acta
Neurochirurgica, 160(6), 1235–1242. https://doi.org/10.1007
/s00701-018-3519-7
You can find more information about the APA format and citation style at the links below.