This refers to the Title Tag that is displayed in the browser tab and in the source of your Page between the <title> tags. It is enabled by default and the formats shown in the Format fields below control how they will appear (see below).
Title Format Fields
The Format fields control how your Title Tags will be formatted for each type of content. These settings can be changed if you wish. The supported formats are shown in the inline documentation for each field. Leaving them as default would, for example, output a Title Tag for a Page as “My Page Title | My Site Title”.
A list of available macros for each specific Title Format field can be found in the inline help for each field as shown below: