Trying to understand VLANs (port-based Vs. 802.1Q)

I'm trying to understand the differences between port-bases & 802.1Q VLANS.
I've done a bit of Googleing but really cant see why I would use one over
the other.

If I understand it correctly, port-based is down and dirty. The devices in
the list can access these other ports.
VLAN1 - 1 2 3
VLAN2 - 4 5 3
VLAN3 - 6 7 3

Above, each port would see one other port, and everyone can see port 3
I think I have the above concept clear. So now onto 802.1Q.

I've got the part about tagging or untagging outgoing packets, but am not
clear about the incoming packets *tagged, or untagged) and how that works
exactly. Also why/what advantages are there to this method over port based.

Thanks

 

802.1q allows multiple vlans to pass over a single connection between devices. If you want 10 vlans to go between 2 switches you use 1 cable and configure both switches to pass all 10 vlans over that one cable.

If we didn't have clan tagging the above example would use 10 ports on each switch to get all10 vlans over to the other switch.

Does this help?

Scape