Connection Pooling

Connection pooling being normally used in web-based and enterprise applications is usually handled by an application server. Any dynamic web page can be coded to open a connection and close it normally but behind the scenes when a new connection is requested, one is returned from the connection pool maintained by the application server. Similarly, when a connection is closed it is actually returned to the connection pool. Connection pooling was first introduced in Microsoft Internet Information Server 3,[citation needed] the idea was soon after incorporated into other software vendors web server products.

http://www.15seconds.com/issue/040830.htm
http://www.ondotnet.com/pub/a/dotnet/2004/02/09/connpool.html