@@error is a sql server variable which returns error number generated by last query.

Example:-

if u run a query and this return error and can't execute.so in long procedure it is much important to rollback transaction .
Declare @@error_return as  int
update table_1 set name='Ais' where employeeid='HOM0044' and lastname like 'Singh%'
set  @error_return=@@error
if @error_return>0
---rollback tran
else commit tran

Dear Raj Kumar
   @@Error is System Variable in Sql Server

Heloo Friend!

This is sql server keyword to represent the error occures during any excution of sql statement and it has 0 for no error ,it has various number for various type of errors

Thank you!

It is your pl/sql returning variable that returns current line error details.

It is an returning variable in pl/sql that returns the error for the current line.

@@ERROR Returns the error number for the last Transact-SQL statement executed.
When SQL Serversuccessfully completes the execution of a Transact-SQL statement,
@@ERROR is return 0 if the statement executed successfully. If an error occurs,
 an error message is returned. @@ERROR returns the number of the error message
until another Transact-SQL statement is executed. You can view the text associated
with an @@ERROR error number in the sysmessages system table.