You can send things to a method

Just as you expect from any programming language, you can pass values into your methods. You might, for example, want to tell a Dog object how many times to bark by calling:

d.bark(3);

Depending on your programming background and personal preferences, you might use the term arguments or perhaps parameters for the values passed into a method. Although there are formal computer science distinctions that people who wear lab coats and who will almost certainly not read this book, make, we have bigger fish to fry in this book. So you can call them whatever you like (arguments, donuts, hairballs, etc.) but we’re doing it like this:

A method uses parameters. A caller passes arguments.

Arguments are the things you pass into the methods. An argument (a value like 2, “Foo”, or a reference to a Dog) lands face-down into a... wait for it... parameter. And a parameter is nothing more than a local variable. A variable with a type and a name, that can be used inside the body of the method.

But here’s the important part: If a method takes a parameter, you must pass it something. And that something must be a value of the appropriate type.