What is a timestamp? How do timestamp-based protocols for concurrency control differ from locking based protocols?

What will be an ideal response?

Timestamp A unique identifier created by the DBMS that indicates the relative starting
time of a transaction.
The use of locks, combined with the 2PL protocol, guarantees serializability of schedules. The
order of transactions in the equivalent serial schedule is based on the order in which the
transactions lock the items they require. If a transaction needs an item that is already locked, it
may be forced to wait until the item is released.
Timestamp methods for concurrency control are quite different; no locks are involved, and
therefore there can be no deadlock. Locking methods generally prevent conflicts by making
transactions wait. With timestamp methods, there is no waiting; transactions involved in
conflict are simply rolled back and restarted.