Netmask are contiguous bits, wildcard masks don't need to be.
The former is accurate for defining subnets and the latter is useful for
describing ranges for firewalls, route maps, or other such things.
example:
10.0.10.0 is nntp1.domain.com, 10.0.11.0 is nntp2.local.com
access-list 185 permit tcp any gt 1023 10.0.10.0 0.0.1.0 eq nntp