What does 'parent interface' mean with respect to VLANs?

Question

I'm trying to learn about VLANs by configuring a router with PFsense installed.

Reading the documentation I came across the following sentence:

The following example shows how to configure two VLANs, ID 10 and 20, with igb0 
as the parent interface.

(Source: https://www.netgate.com/docs/pfsense/book/vlan/pfsense-vlan-configuration.html )

I googled 'igb0' and found the man page which states:

 igb -- Intel(R) PRO/1000 PCI Express Gigabit Ethernet adapter driver

From this I assume that igb0 would relate to a PHYSICAL gigabit Ethernet interface on a router. And based on this assumption I infer that "parent interface" means; the physical interface to which one or more VLANs is associated. Therefore, any device connected to VLAN No. 10 (ID10) or VLAN No. 20 (ID 20) will need to be physically connected to this physical interface?

Physical Example: Router(igb0) -> Switch -> Devices on VLAN(ID=10) & Devices on VLAN(ID=20).

Are my assumptions correct?

Answer 1

As you've already guessed, the parent interface is the physical interface the virtual subinterfaces are created on. It's the one doing the actual transport to other physical devices. The igb0 bit most likely refers to "interface gigabit b0".