You need a router. There are two main types for home use. One is wireless and the other wired.
In either case, the router plugs into your phone line. You can then use two ethernet cables to plug into the router and your PC and laptop.
However, if your PC and laptop are wireless enabled, you could use a wireless router.
As a cheaper method, if your PC is able to connect to the internet, you could simply plug an ethernet cable in the back of the PC, plug the other end into the laptop, and change the laptop settings to 'Connect via another computer'.