parameters aren't the same as variables?
No. When calling a function, it can take values/objects as input, those are called the parameters (or arguments) of the function. They are indicated between parenthesis after the function name in the function declaration. For example, the function void func(int a, int b) takes 2 integer parameters, which are assigned to variables a and b inside the function when calling it.
Zen covers it excellently, no more to be said here.