The topic caption is the title of the topic displayed in the TOC, both in Help+Manual and in your output. For example, captions are displayed as the TOC titles in the Contents pane of the HTML Help viewer and the Contents page of a PDF file.
When you create a new topic the caption text is duplicated in the topic header, which is the title displayed in the editing box above the topic itself. The header is also displayed in your output, for example above the topics in the HTML Help viewer.
See also: