PVID is an acronym for “Port VLAN ID”. In IBM switching products, the term PVID is used to identify the VLAN ID that is used to process traffic within the switch when the packets do not have a 802.1Q VLAN tag.
The terminology is different, but the concept is the same as other networking products. To put this in more industry standard terms, the Port VLAN ID is the “native” or “untagged” VLAN.
When an untagged packet is received on a port on a switch, PVID tells the switch to “treat packets received on this port a belonging to this VLAN ID”.
When packets egress the switch on the port, the switch will remove (or not apply) a VLAN tag if the packet belongs in the PVID VLAN.