If i have a VLAN (say VLAN 10) on switch 1 and again a VLAN 10 on switch 2. Can the hosts on these VLANS communicate with each other?
Yes, assuming the switches are connected together and VLAN 10 is forwarding on the connected ports. Both ports have to be configured the same, so that VLAN 10 is either tagged on both or untagged (native) on both.
yes, however they must be conected with a trunk link and allowed the same vlan's, don't forget to set the link as trunk