What is difference between datetime and timestamp

Solution 1:

One is a date and time, the other is a column type that is updated every time a row is updated.

[Note timestamp is being deprecated; use rowversion instead]

Solution 2:

Timestamp (deprecated synonym for rowversion) :

Is a data type that exposes automatically generated, unique binary numbers within a database. rowversion is generally used as a mechanism for version-stamping table rows. The storage size is 8 bytes. The rowversion data type is just an incrementing number and does not preserve a date or a time. To record a date or time, use a datetime2 data type.

http://msdn.microsoft.com/en-us/library/ms182776.aspx