The joystick is an input device consisting of a stick manuevered by the user through electronic signals.
There are 2 types of joystick: digital joystick and analogic joystick.
This is a diigital joystick
The joystick digital is able to establish only one direction, that also allows analog intensity gradual variations of the thrust in any direction. For example, the player of a video game can make the move more or less rapidly the character.
This is an analogic joystick
An analog joystick (or analog stick, when it refers to the single lever) is a joystick which transforms the movement of the hand to an analog electrical signal.