Netgear is a bit special for the naming conventions about VLAN & Trunk.
Here is the explanation:

I agree it's a little confusing, and I cannot think of a case where the two values wouldn't match. Enterprise-grade switches don't seem to have this problem.

EDIT:

Netgear (and Dell) use some confusing terminology. But the principles are the same for any VLAN-capable switch:

VLANs are identified by number, and that is the PVID. So "vlan 6" has PVID = 6.

VLAN tagging is done per port. So a VLAN can be untagged on one port, but tagged on another.

If a port has only an untagged VLAN, then we call it an access port. The PVID is not part of the Ethernet frame that's sent out the port. Frames received on that port are put into the untagged VLAN. If the untagged VLAN is 6, any untagged frame received on that port is put into VLAN 6.

Cisco calls an untagged VLAN a native VLAN. It's just a different term for the same thing.

If you don't specify an untagged (native) VLAN on a port, then the untagged VLAN defaults to VLAN 1 (PVID=1). This is what Dell and Netgear mean by "default" VLAN: the VLAN that's assigned if you don't specify one. That is NOT the same as Native VLAN (see above). VLAN 1 can be tagged or untagged on a port.

If you tag a VLAN on a port, it's called a trunk port (Cisco term). Trunk ports are usually used to interconnect switches. Most PCs don't understand tagging since a tagged frame is a different Ethernet format. You can have as many tagged VLANs on a port as you like. But the port can have no more than one untagged VLAN. You can also disable untagged frames on a trunk port.