Realtek is a ethernet NIC (network Interface card) on the back of your PC case you will see the standard dialup port, look around for another that is a bit larger, that is your ethernet port that you will use to hook your DSL modem to via a CAT5 ethernet cable.

The 1394 is your firewire port that you use to hook a digital camera up to and download your video through.

Hope that helps,
BB