Creating and Maintaining Home Networks

  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.
            Modem                         Router

  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 
  Using your browser type:
  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.