If I remember right the pc sends a DNS request which goes over ethernet to a DNS server. The DNS server sends the IP of the website host back and the the pc sends a request throught the ethernet and firewall, then to a router that sends the request through some more routers along fiber optic cables until it reaches the host of the website. Then the host sends back the website data with a '200' for ok or a '404' if there was an error.
I think thats the general idea.
PC => DNS
DNS => PC
PC => firewall => routers => host
host => routers => firewall => PC