This command displays information about the access-lists that are configured on a router. It also shows information about what lines are matching in the ACL.
Router#show access-lists <number or name>
In the below example we use show access-lists to see what access-lists are configured on R1..
R1(config)#do show access-list Extended IP access list 102 10 deny tcp any any gt 1024 20 permit ip any any (4062 matches)