A common setup for having Internet service is a line into the property to a Modem with a connection to a Router which is then connected to a computer. Having a Wireless/Wi-Fi Router allows a computer to connect to the Router without using a cable. My LAN/Local Area Network has a PoE Modem provided by my ISP connected via Ethernet cable to my Wireless Router. The Router has an Uplink port to the Modem, a connected 8-port Switch, 5 Desktop computers via cable, 2 printers via cable and a NAS drive via cable. I can have computers connected via Wireless/Wi-Fi, now with 3 Notebooks in use.
Whether a Router includes the Modem is possible, some ISPs furnish that type or a user can purchase their own.
The first thing my ISP asks me to do with no service is to plug the PoE Modem directly into the RJ-45/Ethernet port on a computer to check if there's Internet Service available, if so then I have to do a speed check from a link on their main page. That cable change bypasses the Router to eliminate a possible issue.
With a Wireless connection the age of the Router and the adapter in the computer may be an issue, newer ones have a choice of 2G and 5G speeds while older ones will be only 2G. There's even faster on the horizon. My connection on this Notebook, 2G may or may not be shown on the name but 5G always is when available: