As you work in collaboration with other users, you might encounter items that are locked by other users, either because they are being edited by another user, or a draft item has been created.
Locked items
When a user is editing an item,
the item is locked to other users. This means other users cannot edit
the item until the current user closes the item that is being edited.
A lock symbol 
is displayed against items that are currently locked.
Users with administrator access can unlock items currently being edited by a user by selecting an item and then clickUnlock.
Users with manager access can also unlock items so long as they have manager access to both the item and the library it is stored in.
Hierarchical item lock options
Locking of site areas, taxonomies, and categories are configurable and is not enabled by default.
When locks are enabled for site areas, you cannot create any children within the locked site area. For example, if a site area is locked, you cannot create any site areas or content items within that site area until it is unlocked. This restriction applies only to direct children of a locked parent. Items that are descendants of a child of a locked parent are not affected.
Draft items
When a new draft of a published item is created, a tick is displayed against the published item. This means that no other user can create a draft until the current draft progresses through a workflow and its state changes to published.