The company that sells you your internet connection.
Like the road that connects your building to the highway: everything you send and receive travels over it.
A seven-person office had one internet line and a card machine that needed it. A cut cable on the street took the line down for most of a day, and every sale had to be written on paper.
Network covers the firewall and switch behind the provider's modem, which is where a business office takes over from the provider's equipment.
Who do I call when the internet is down?
Check the modem lights and restart it first. If that does not help, call the provider, because the fault is often on their side of the wall.

Every WILDCARD card exists to solve one named problem. Find yours.