Yeah, "f(x)" is the same thing as "y=" we just stop using "y=" because f(x) is a much better representation. Because sometimes we will have to deal with more than one function, so we give names such as, f(x), g(x), h(x), etc. You probably already know this. Later on you will learn to do all kinds of things with functions, such as transformations, compositions, and many other things...