I am not familiar with cable internet, so bear with me! Have a new house where cable service in each bedroom and den. Can internet be ran through all cable connections or do you have to use wireless?

internet can't go to every room via the cable company. You pick one room, they put a filter on, and you connect your router to the provided cable modem. Follow the routers instructions for setup.

You do this AFTER the cable guy has connected your pc, got it internet and has left the building.

Imagine the power if you knew how to internet search

Okay a "filter" is what? How does the signal get from there to the other computers?

Short answer: You cannot use your coax cable in lieu of a "real" network.

Longer answer: I suppose you could, but that'd require special hardware, and there's no guarantee it'd work, as the coax network model was designed for a series of connections, and not a line splitter. It'd also require your coax being disconnected from the cable company's grid.

Unless you have cat 5 wiring to a common point where your cable modem is located you will have to get a wireless router and however many wireless nics for your devices you get them on the network.

Thanks "vipergg". I understand your answer.

Like Wanderer said on the 1st response, Once the 1st PC is connected via the cable modem "The Cable Guy" sets up for you...
You can connect a router or switch to the cable modem and from there split your connection to the rest of the computers in the house.
If the router you use is a Wireless Router you are also going to need wireless cards on all the other machines or you can get a wired router and lay Cat5 cable to the other locations in the house. If you buy a wired router always get one with a few extra ports than what you need for future add ons.
I would go for wireless so I don't end up with a bunch of cable all over the floor. Hopefully is only a one floor house because on a two floor house with walls and stairs and... connectivity might be low.
Just some things to think about.

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a filter... here is a basic electronics lesson.
You can have multiple fequencies going down a single wire like your cable. In your case cable can provide TV, Internet and VoIP [telephone]. These are three diffent signals going down the same wire. A filter filters out everything except the desired signal. In your case of internet it would filter out the tv and voip signals so the only input the cable modem would get is the internet signal.

Imagine the power if you knew how to internet search