Affiliate Marketing Secrets

How does establishing an internet connection usually work, not just in the U.S. but around the world?
I’m currently studying in China, in the previous year, I was able to simply connect a cable from the internet port in the wall to my laptop. After that I would have to enter an account name and password, PPPOE.
Which makes me wonder about what a router actually does. The place I’m currently living in has just been built, the major internet line hasn’t been set up yet. I’m curious as to how I would go about setting up the connection.
Previously it seemed I had to buy these cards w/ the account name and pass from specialty stores, the cards were affiliated with the school. As the “dorm” i’m currently living in has no affiliation with the school it seems I have to go register something…not too sure on the details.
So, what does a router? Would I need one? Where does that “internet port” in the wall actually lead o.0?