Not everyone wants to eat hamburgers.

We could write a new function for each new sandwich type, but that takes a lot of work and risks making mistakes.

Instead, we’ll generalize the hamburger function to a sandwich function. This new sandwich function will still make a bread-topping-topping-bread combination, but the toppings may change based on inputs to the function:

function makeSandwich(topping1, topping2) {
  Add bread
  Add topping1
  Add topping2
  Add bread
}

We’ve renamed the function makeSandwich() and given it two inputs, or parameters. Each time we call the function, we’ll give actual values for each input, called arguments.

For example, we make a ham-and-cheese sandwich with makeSandwich("ham", "cheese"). We call the function with the arguments “ham” and “cheese”. Those will be the values for the topping1 and topping2 parameters.

Instead of writing a different function for each type of sandwich, we have one function that can make them all!