When you edit an item, the web system will automatically lock that item to prevent others from trying to make edits to it. This prevents people from overwriting each others' changes. Once you have finished editing an item and click the Save button, the item automatically becomes unlocked and is available to be edited by others.
If you attempt to delete an item that’s linked elsewhere in your site, you get a “Potential link breakage” warning, showing you exactly where it’s used. This automatic safety measure is useful in determining just how important a particular asset is to your site. When prompted, you're given the option to delete the item anyway (not recommended), or cancel the action.