Shared components used by Firefox and other Mozilla software, including handling of Web content; Gecko, HTML, CSS, layout, DOM, scripts, images, networking, etc. Issues with web page layout probably go here, while Firefox user interface issues belong in the Firefox product. (More info)
This is the global history which tracks all URLs that a user has visited, across all sessions of the browser. This also includes the history window and link coloring. Examples of appropriate bugs: Chrome URLs incorrectly added to global history, Reproducible crash when sorting by Title in History window, misbehaviour in the History sidebar tab.