Well Netgear make lots of things, but I assume in this case it is a ROUTER.
To use a computer over the phone line for broadband you need a MODEM. But this is only suitable for a single user.
If you want more than one user to use your broadband you need a ROUTER (which also contains a modem).
Also note a MODEM is only any good if you want to plug a wire from your computer into it to get the internet.
But if you want to go wireless from say you laptop to the intertnet then you need WI-FI, and for this you need a router.
So your router gives you two things:
1) The abiity to have more than one user using the internet at a time.
2) The ability to use wi fi.
In the past companies sent out a modem, but nowadays they send out a router as it includes a modem, but has extra features.
I asume Sky would have sent out a set-up CD as well, and this usually makes setting up a router easy. Give it a go.