Extended Access Control Lists (ACL) control traffic by comparing the source and destination address of the IP packets to whichever addresses you have configured within the ACL.

A standard ACL only compares the source address of the IP packet to whichever address is configured in the ACL and allows or denies it based on the ACL, the destination of the packet and the ports involved do not matter. A standard ACL also does not have the ability to filter based on the protocol type, whereas with an extended ACL you can filter IP, ICMP, TCP and UDP packets individually and specify specific ports.