how does a VLAN switch operate and how are MAC frames forwarded?

Question

assume that it conforms to IEEE 802.1Q

Answer 1

So a VLAN is basically a "broadcast domain" and on a switch a VLAN boils down to a specific grouping of physical ports. The current best practice is to have one VLAN per IP subnet. 802.1Q inserts a 4-byte tag into the original frame. The VLAN switch pretty much operates like any other, it learns MAC addresses, builds a forwarding table of which addresses live on which physical ports, it decides when to forward (or drop) frames, and it also typically creates a loop free topology via spanning tree. I assume by "VLAN switch" you mean a multi-layer or layer-3 switch, because that's the last part... in order to pass frames from one VLAN to another, you need some layer 3 device to do this interVLAN routing, typically a layer 3 switch or a router. Check the article below for a full rundown on dot1q.