Each time you quote or paraphrase a source, you must include an in-text citation as well as an entry in your reference list. A direct quote involves copying exact words or phrases from your source material, while paraphrasing involves summarizing someone else's ideas or thoughts into your own words.
What's the difference?
While direct quotes require quotation marks and a page number (or paragraph number if there are no pages), paraphrasing does not.
(See sections 8.10-8.36 of the APA Publication Manual, 7th ed.)
It is important to cite at the appropriate level, meaning you don't want to cite too little nor too much. To learn more about this, have a look at the APA Style site:
Cite both authors (Jones & Smith, 2011).
3 or more authors?
Cite the first author listed plus et al. (Jones et al., 2011).
(See section 8.17 of the APA Publication Manual, 7th ed.)
If you are referring to an author's work that is quoted in a secondary source, name the original author in the in-text citation, followed by (as cited in secondary source, date).
For example, if you want to cite Smith's idea, which you read about in Jones' book, you would provide an in-text citation for Smith's study: (Smith, as cited in Jones, 2002). In the reference list, include a reference only for Jones' book.
(See section 8.6 of the APA Publication Manual, 7th ed.)