More like to connect a computer to a network. If you mean for home broadband, then tamborine is partly right - it could also be used to connect the computer to a router and a router to the modem.
I have one plugged into this laptop and the other end is plugged into the BT black box thingy so that i can accessd the internet, my bult in wireless thing don't work no more it;s died
Many Thanks Guys...it will most likely be used as a connection between a laptop and a desktop pc...does that make sense?...and are Ethernet cables much of a muchness or are they specific?