Inline citations are the components of a citation that are written within the text. These are written shorter to save space and so that the entire citations do not need ot be put into the text of the paper.
Inline citations in a journal (Kay, 2020) are written using the first authors last name, followed by a comma, then the year of the publication, all within parentheses. The previous example was with a single author. If there are two authors, then the inline citation (Kay & Smith, 2020) would be written in this manner. If there are more than two authors, then the inline citation (Kay et al, 2020) will be written using et al. after the first authors last name).