Along with the Host Explorer, Host Custom Lists provide a way to slice and dice your host records using a myriad of possible filters. Custom lists allow you to build your own saved host lists that can be accessed at any time with a single click.
When creating a host custom list, you enter an easily recognisable name, and then attach the one or more filters that make this list special. Your filters are saved so in the future you can view this list with out having to re-define the filters.