Lv1 allows the user to only browse the page. It does not allow the user to edit it. The new page created in Administration Tools allots Lv1 to a Public User by default. This right can be cancelled at any time later. If the page does not allot Lv1 to a Public User, the page can be read only by the allowed Logged-in Users.
What users can do on the page is limited by the Permission Level (1 to 4). A higher level user has access to the functions accessible to a lower level user. It can be set in Page Property Manager. See Permission Level in Page Propery Manager.