There are many aspects of editing related to an editors rank and permissions that will control what can be changed on the map and how editors after them will be affected. Be sure to understand this information to be best prepared when editing the map.
There are many ranking systems in Waze. Each one is used for a different purpose. See this other page for more detailed information on the other ranking systems. The below information is only covering Editing Rank.
A detailed description of locked segments can be found at the Editing restrictions page.