In Sitecore, many users will work parallelly and locking of item will not allow another user to work on the same item. To avoid locking and loss of changes, we have settings in the web.config.
<!-- AUTOMATIC LOCK ON SAVE
If true, the a lock is automatically taken on an item
when a user saves the item.
<setting name="AutomaticLockOnSave" value="false" />
<!-- AUTOMATIC UNLOCK ON SAVED
If true, the a saved item is automatically unlocked after
<setting name="AutomaticUnlockOnSaved" value="false" />
Both the setting should be true; former to avoid data loss and latter to avoid locking of items.