When you press the connector button, a pop-up will appear on the screen showing the connectors. It also appears when you close the trap door for the connectors. If you're trying to close the door but you forgot to take out all of the cables, the software will recognise this and prevent the closing process from starting, warning you that you need to remove the cable(s) first. When the laptop gets above a certain temperature it will automatically open the door to improve cooling, kind of like an expensive sports car.
The pop-up indicates that a connector is in use.
The connectors can (simultaneously) be used for connecting external drives at their maximum speed. The number of available products that feature a Thunderbolt connectors is still very limited, but you can expect to see docks and even external graphics cards taking advantage of the fast connection. You could also use them to connect the laptop to a network using Apple's network cable adapter for Thunderbolt, provided you get the necessary Windows drivers.
The special button for extending the connectors.
While the motorized trap door approach is a very innovative and unique solution, it's too bad Acer did not include more connectors. It would have made sense to include a VGA port and network port. The only difference between the S3 and the S5 is the additional Thunderbolt port, in terms of connectors.