A modem, usually provided by your Internet Service Provider
(ISP) translates signals from your ISP via fiber, cable,
phone line, or Antenna into digital signals using the
internet protocol (IP). A modem will have a unique IPv4
address on the Internet.
The current status of the modem lights helps the end user to
know whether a connection is established, if the connection
is active, or if the connection has dropped for some reason.
One should download the Manual (PDF) for your Modem.
Cable modems often use an internal IP Address 192.168.100.1
Using your browser type: http://192.168.100.1
Phone line DSL and Cable Modems often look similar. Fiber
Modems are quite different. Elon Musk's Starlink Modem is
built into the antenna transparent to the user.