The following sections: APA, 7th and 6th editions, and Plagiarism, will go into specifics. For now, a general introduction to the concepts behind citing our sources and avoiding plagiarism may be helpful.
We cite sources we use in research to be fair and ethical. Almost all research is built upon previous work, so acknowledging that previous work is important, just as it will be important for future researchers to acknowledge any contributions we may make to a field of study. Think of scholarship as an ongoing conversation: we build on what came before us; future researchers will build further upon our work. Citing those sources does not detract from our work, it actually provides credibility. Failure to cite the sources we used, even if paraphrased, implies that those ideas or concepts expressed are our own, which is dishonest.
Another aspect of citation is that we are providing our readers with sufficient information to locate the sources we have used, in case they wish to read the entire article. This also contributes to scholarly conversation.
Many databases have citation generators built in, which are helpful and can save time, but these database-generated citations are generally not completely accurate. If you rely upon database-generated citations, always check them against the appropriate citation manual, and correct as needed.