Hi Martin, the primary password protects your saved logins. They cannot be viewed or autofilled until that password is entered. The primary password does NOT affect any other aspect of browsing or using Firefox.

You are looking for a way to prevent people from starting Firefox, or preventing them from seeing your history/bookmarks if they do start Firefox? There isn't a built-in feature for either of those, but there are some creative methods you could try if other people use your computer and they share your Windows login...