HVLAN is kind or port-based VLAN where all VLAN intersects on one port (or group of ports), which named “uplink port(s)”.
Let's imagine we have 5-port switch with 3 customers and 2 servers/routers:
|Port no.||who connected|
and want customers to “see” both server and router, but not to “see” each other. On the other hand, server and router must see everyting, without any restrictions. We can configure this scenario using HVLAN with two uplink ports and two restricted ports. See here:
|Port no.||who connected||port-type|
This setup is commonly used, when PPPoE is implemented to deliver internet connectivity to customers thru cheap ethernet switches of DSLAMs.