What's the point of the () in :LoadCharacter()?

That calls the method.

They're arguments, not parameters, but you've got the right idea. Parameters are a function's input variables. Arguments are values passed to a function during a function call, and which get assigned to parameters.

So, basically when defining the function, you have parameters... hmmm

Yes, parameters appear in the parentheses of a function definition, not a function call. e.g, function add(a, b) return a+b end. a and b in this example are parameters, whereas 2 and 3 in local sum = add(2, 3) are arguments.

Thanks for explaining.

Think of it like this: local new_obj = Instance.new("Part",workspace) -- You see you may need to put arguments in it.