Background scripts or a background page enable you to monitor and react to events in the browser, such as navigating to a new page, removing a bookmark, or closing a tab.
In Manifest V2, background scripts or a page can be persistent or non-persistent. Non-persistent background scripts are recommended as they reduce the resource cost of your extension. In Manifest V3, only non-persistent background scripts or a page are supported.
Right click and go to setting.
Left click and the popup.