Unfortunately, it is a common practice to create a 'heading' by highlighting the text and applying a different font, a larger font size, bold formatting, etc. However, this only works if Word's Heading styles are used. For example, screen reader users can access a list of all headings in the document, jump from heading to heading, or even navigate by heading levels (e.g., all second-level headings).
Screen reader users can also navigate Word documents by headings. When encountering a lengthy Word document, sighted users often scroll and look for headings to get an idea of its structure and content.
A good heading structure is often the most important accessibility consideration in Word documents.
