Inbound Filters is a setting commonly found on broadbandrouter firmware. Inbound Filters are used to limit access to a server on your own network. Filter rules can be used with virtual server, port forwarding or remote administration features.
See “Common Router Settings” in the Quick Reference section of Webopedia.
See also Webopedia’s “Did You Know… Routers, Switches and Hubs: What’s the Difference?“