The @sindy post: RouterOS bridge mysteries explained that @mkx linked is excellent.
When I was learning the MikroTik vlan-filtering bridge, it was one of the most helpful resources for me to wrap my head around how to logically map what the bridge “entity” was, coming from EdgeRouter X vlan-aware switch0 and Cisco.
I have added a bit to what @sindy’s post has, with respect to the internal trunk link between the switch and the CPU. My additions are in these posts, post #16, post #18, and post #19 from this thread Slow Hex file transfer speed. You may want to skim the thread, there are other posts there too with some hypotheses about hidden (archane?) interactions in the bridge virtual connections between the CPU and the switch ASIC.