By default, new topics always have a "header", displayed in a separate editing box above the main topic editor. You can turn the header off with the options menu in the top left corner of the editor window if you want. This turns off the header for the current topic.
Initially, this header contains the title of the topic, formatted with the standard Heading1 style and with the background color set in the HTML topic page template. You can also add other content, including graphics, hyperlinks etc.
Header formatting, background colors and additional content are only supported in electronic help formats (HTML Help, WebHelp, eBooks and Visual Studio Help). ePUB eBooks have limited or no support for additional content. In print-style formats (PDF, DOCX, printed manuals) only the plain text from the header is exported when you publish and the formatting is defined separately