What is a Flooding Domain?

I have been working on configuring this Ciena 3906MVI premise router, with a Virtualized Network Function (VNF), and connecting that VNF back to some physical network ports.

This is a rather complex piece of hardware (under the hood).

I noticed in some commands, they were creating these Flooding Domains. And I didn't know what those were (there were sub-types called VPWS and VPLS and I need to look into that as well).

These Flooding Domains are then associated with "classifiers", like "Ingress Classifiers".

I didn't truly know what a Flooding Domain was. Not a lot on the web if you search those two words together. There's plenty of stuff on the concept of Flooding, however.

I found a link where someone asked what the difference between Flooding and Broadcasting is, and it is in this link where I found the best clues to get the proper understanding. So I will recap that there:

https://networkengineering.stackexchange.com/questions/36662/what-is-the-difference-between-broadcasting-and-flooding

What is the Difference between Broadcasting and Flooding?

Broadcasting is a term that is used on a broadcast domain, which is bounded by layer-3 (routers). Broadcasts are sent to a special broadcast address, both for layer-2 and layer-3. A broadcast cannot cross a layer-3 device, and every host in a broadcast domain must be interrupted and inspect a broadcast.

Flooding is used by a switch at layer-2 to send unknown unicast frames to all other interfaces. If a frame is not destined for a host which receives it, the host will ignore it and not be interrupted. This, too, is limited to a broadcast domain.

Flooding in OSPF (layer-3) means that the routes get delivered to every OSPF router in an area. It really has nothing to do with a broadcast. OSPF doesn't use broadcasts to send routes, it uses unicast or multicast to connect with its neighbors. Each OSPF router needs to have a full understanding of all the routers and routes in its area, and it tells all its neighbors about all its local routes, and any routes it hears about from other neighbors. (OSPF routers are unrepentant gossips.)

So, a Flooding Domain is essentially a "domain of packet delivery" - where the point of the inbound (ingress) packet is not where the packet exits (egress). That's my best definition.