To appear skilled in the art can be defined both saying the digital electronics uses discrete values with magnitudes, while the electronic analog magnitudes used with continuous values.
To understand we can also say that a Digital Inputs states we measured 1/0, ON / OFF, ON / OFF, while an Analog inputs can measure broader values such as voltage 3-5 volts with all intermediate values.
With this earthly definition be easy to realize that I know a digital input via GPS device if the engine is running, if a door is open or closed or if the alarm has been triggered by robbery.
Basically, the GPS Trackers offer us 1 or more entries which connect the positive cable that will power when one of the two two events (on / off) occurs.
This is the conceptual starting point. As the GPS Tracker is more complete we will find more Digital Inputs, variable states of on / off with positive or negative charge and are more able to withstand more voltage or amperage for each entry.