Access-lists ?

Hi,

This is my first post..
I need some details regarding access-lists in particular with protocol parameter.
In some cases, for denying a host it is used as ip while in other it is as tcp/udp.
what must be actually used for denying a host and a network?

Also, see the below lists;

access-list 101 deny udp any any eq netbios-ns log
access-list 101 deny udp any any eq netbios-dgm log

Pls explain about the port nos used here.