# What is f(x,y) in Digital Image Processing?

I am a novice in Digital Image Processing, and while reading the book of DIP by Gonzalez and Woods, I find that they have represented digital image as $$f(x,y)$$ but nowhere it is mentioned what is $$x$$ and $$y$$ actually that we are passing to the function $$f?$$ Does $$f(x,y)$$ represent the intensity of the points located at point $$(x,y)$$, so does $$f$$ actually returns the intensity of the pixel at that point or is it something else that I am missing?

f( x, y ) gives the intensity of a channel at position (x, y)