|WAN = Wide Area Network |
So yes, it's a term. With regard to the actual connection on a router (SOHO or otherwise) the connector itself would be an RJ-45 port and is also referred to as the "external" connection. The clear plastic connector/plug at the end of a network cable is in fact an RJ-45 connector. The type on a telephone cord is an RJ-11.
Most SOHO routers, if you look at one, will have one port marked "internet" or "WAN" for the connection to your highspeed modem. There will also be one or four "LAN" ports (LAN = Local Area Network) which are also RJ-45 ports.
As wanderer said, if you're going to cable some or all rooms in your house, it's best to use a Patch Panel at the end where your router and switch(es) will be. Make sure you get one spec'd for the type of cable you're using (Cat5e/Cat6). Instead of having loose cables hanging out of your wall, I would run them to outlet boxes and get some faceplates for RJ-45 "keystone" type connectors. The term "keystone" may actually be a brand name but is used generally to refer to the types of RJ-45 connectors that snap onto a faceplate.
If you don't have available outlet boxes you can always buy (at most any hardware store) outlet inserts that all you need to do is cut the right size hole, fit it in and screw it in place then attach the faceplate to it.
The only tools you'll need for cabling will be side cutters, a stripper (or utility knife if you're VERY careful not to score the covering of the actual wires when cutting the cable casing) and a punchdown tool (for network cables).
Lastly, you'll want to have all your cables tested and certified. This can be done by most any electrical contractor or specalized network cabling company. I'd call around and get quotes based on the number of runs you'll have when you're finished.