Some instructors will ask you to use the "headings and subheadings" system of formatting for your papers. This is most typical in the social science courses that use APA citation style and is a way to organize the content of your paper and make it more accessible to your readers.
Each major section of your paper will begin with a heading, appropriately formatted. If there is more than one main idea within the section, then you will use subheadings to further delineate the content.
APA style allows for up to 5 heading levels, each with its own formatting style. See the Format of Headings chart on the APA Style Site for details.
To make your headings accessible to readers who might need a screen-reader or other assistive technology, your word-processor (i.e.,WORD) has automatic headings functions to make them easier to create. Check the formatting against the chart above.
The screenshot below has examples of a paper with 4 levels of headings.
Subheading 2 indicates 2 sections that are part of the content in heading 1; subheading 3 indicates two parts that are subsections of the second subheading 2, and so on. Notice that the title of each subheading is indented and formatted specifically to indicate what level of subheading it belongs to.
Note: Not all papers require this type of formatting. Check your assignment requirements or ask your instructor for any particular details they want for your papers.
Adapted from: "Heading Levels Template: Student Paper" by APA Style, n.d., (https://apastyle.apa.org/instructional-aids/heading-template-student-paper.pdf)