Why don't I need to use port-forwarding for commands to reach my imp?

My Imp is behind my router and has an IP address on my home network (of course). Normally for unsolicited information to enter my network and reach a device, the request has to come with a specified port and I need to configure my router with port forwarding to make sure the request gets to the right device. So how do inbound commands make it to my Imp? There is no special Imp software running on my machine and I don’t have port forwarding enabled. But it works!! Can anyone tell me how?

It works because the imp always makes an outbound connection to our servers; the server can then forward data sent to it down this already open connection.

Ahh…now I see. Thanks!!