What does the caption tag do in HTML tables?

The caption tag in HTML tables serves a specific function: it provides a means to include a descriptive title or explanation that is visually associated with the table. When used, the caption appears at the top of the table by default, giving users context about the data that follows. This is particularly helpful for accessibility as it allows screen readers to convey important information regarding the table's content, enhancing the overall user experience.

The other options suggest functionalities that do not align with the purpose of the caption tag. For example, the first option pertains to image maps, which are not related to tabular data. The second option suggests defining narrative elements, which is typically not relevant to the structure of a table. The last option references self-containing text—this is not applicable to the caption tag's role. Thus, the accurate understanding of the caption tag as a descriptor of the table is encapsulated in the function of allowing a table description to be placed near the table.