Hi Jyotsna,
   
please check out the following allinterview URL for 
concurrency testing ..
<a 
href=http://www.allinterview.com/showanswers/137>Concurrency
 Testing</a>

Multi-user testing geared towards determining the effects 
of accessing the same application code, module or database 
records. Identifies and measures the level of locking, 
deadlocking and use of single-threaded code and locking 
semaphores.

which is nothing but load testing.where we apply all user 
operations at the same intanse.

if it is wrong plz give ur answere

Multi-user testing geared towards determining the effects of
accessing the same application code, module or database
records. Identifies and measures the level of locking,
deadlocking and use of single-threaded code and locking
semaphores