Following is a path to help understand Vlan:
1. You may connect hosts to ports of switch. Basically all of them belong to one Vlan. If you connect 2 switches, you can reach hosts connected to the second switch if they are ine the same Vlan. So hosts are in the same 'broadcast domain'.
2. You may create Multiple Vlan and assign ports to those Vlan. Hosts attached to ports belonging to SAME Vlan can reach each other.
3. Between Vlans, if you route the traffic, so one host in one Vlan can reach another one hooked in another Vlan.