Connection Pooling:-
Connection pooling reduces the number of times that new 
connections need to be opened. The pooler maintains 
ownership of the physical connection. It manages 
connections by keeping alive a set of active connections 
for each given connection configuration. Whenever a user 
calls Open on a connection, the pooler looks to see if 
there is an available connection in the pool. If a pooled 
connection is available, it returns it to the caller 
instead of opening a new connection. When the application 
calls Close on the connection, the pooler returns it to the 
pooled set of active connections instead of actually 
closing it. Once the connection is returned to the pool, it 
is ready to be reused on the next Open call.

connection pool is set of active connections object,so that 
someone else can make use of it without waiting of creating 
the new connection.The number of connections allowed to a 
particular database may be limited due to server capacity 
or database licensing restrictions.

when a connection opened first time the connection pooling 
is created , and is based on the exact match connection 
string given to the connection object. 
It works only the connection string is same.otherwise it 
will open a new connection. Hence connection pooling 
maintains all these coneections to made the retreive of 
data effectively and fastly.