Citation shows your readers where you got your information to give credit to the original authors and also gives your readers the means to find sources that might be of use in their research, too.
Citation formats, known as styles, vary by discipline (and often by journal) based on what each discipline finds most important in terms of how and what is cited. Style manuals usually contain information about preferred terminology and paper structure in addition to how to cite sources in the specific format of the style.
First-year students must use MLA in CAL 103 and 105.
Look for your discipline in the Purdue OWL list here or check the selected styles highlighted below.