You read it right. So today I learned that we can apply a material on selected faces in an object using "apply" button. I was believing that I could do the same with modifiers and particles but I couldn't find the apply button or any other thread that related to it. So it would be the first thread talking specifically about this and I hope any other beginners will find this thread useful.
Bear with me on this: I am ignorant beginner and I never read the manuals