In computer programming, a parameter or a formal argument is a special kind of variable used in a subroutine to refer to one of the pieces of data provided as input to the subroutine. [https://en.wikipedia.org/wiki/Parameter_%28computer_programming%29#Parameters_and_argumentsen.wikipedia.org/wiki/Parameter_%28computer_programming%29#Parameters_and_arguments]
A parameter is a named variable passed into a function. Parameter variables are used to import arguments into functions. [mozilla developer network]
Note the difference between parameters and arguments:
Function parameters are the names listed in the function's definition.
Function arguments are the real values passed to the function.
Parameters are initialized to the values of the arguments supplied.