Simple definition
A tombstone represents a deleted Active Directory object retained temporarily to replicate its deletion.
Purpose and use
An AD tombstone retains a reduced representation of a deleted object so deletion can propagate to other replicas.
How does it work?
Selected attributes are removed, and the object remains for a directory-configured period before cleanup.
Example and verification
For an apparently returning deletion, inspect controller state, offline duration and deletion propagation.
Points to watch
A tombstone is not a complete object backup. The deletion lifecycle differs when AD Recycle Bin is enabled.
In short
Temporary retention supports replication consistency; recovery depends on additional states and mechanisms.