Lost and Found

Lost and Found container is a special pourpose container in which You will find objects, which for whatever reason has lost its parent. So if you will delete OU at one DC and at the same time create object in this OU on another DC or move objects to this OU before replication of OU deletion will occur, after replication You will find them in Lost and found.

If You will bring back to life deleted object and You will not restore OU in which it was located - this object will end up in Lost and found.

So if you will find objects there, before You will delete them think why they end up there ... in most cases probably You will want to preserve tham and move somewhere in your directory.