Instance Variable: An instance variable is declared within a class but outside any methods, and it belongs to an instance (object) of that class. It can be accessed by any method within the same class.
Parameter: A parameter is a special kind of local variable used in method declarations to receive values from outside when calling that method. It allows data to be passed into methods.
Global Variable: Unlike local variables, global variables are declared at the beginning of the program and are accessible from anywhere in the code. They have wider scope than local variables.