Digital land line vs an old style land line

Mainly digital service plugs into a modem where traditional plugs into a wall jack. Digital has many more options than traditional. See this topic

Digital Land Line is basically VOIP service.  It requires that your Internet Gateway maintain power to operate.

Traditional Land Line is a local loop Analog service, i.e. POTS.  It works when you lose power, etc.  It is typically more expensive now, with fewer features.