So, three replies and I know everything:
Phone jack/line<-->1 Modem<-->1 WAN port<-->1 Router<-->1 LAN port<-->many devices into many jacks on the LAN port or router.
There are two-in-one modem/router combos. Wow!
Looks like I'm going to need the net provider to sell me the modem to connect to the internet. Then the rest will be my choice whether to expand to more devices or to try to access office from home.
I'll get the modem first and show you guys the picture on here so I know whether to pay for a router, too, or not. Stores have those 30-day trial or return policies. If I make a mistake, I'll return what I've bought within a week or so.
Thanks, Jimmy, Midnight and slude.