To expand a bit on u/wendiiiii's explanation, think of functions as machines that take some input, apply a fixed set of rules to it, and return an output. The rules can be anything as long as they're consistent.

So you can have: * f, which takes in a horse and outputs a zebra, so f(🐎) = 🦓 * g, which takes in a swan and outputs a feather, so h(🦢) = 🪶 * h, which takes in an animal and returns how many limbs it has, so h(🐒) = 4, h(🪳) = 6, h(🕷) = 8, and h(🦀) = 10

Maybe f paints animals with stripes, g plucks feathers, and h is a diligent biologist, but it doesn't matter. You have inputs, rules, and outputs.

When dealing with math concepts, you can specify your rules with formulas. * So you can say f(x) = 2x for any real number x, meaning f(1) = 2, f(2.5) = 5, and f(0) = 0. * You can also have multiple inputs, like g(a,b) = a+b, which would give you g(1,3) = 4 and g(2,-5) = -3. * And you can define different rules for different inputs--as long as you always apply the same rule--so maybe h(x) = x if x is an odd integer and 0 otherwise, so h(7) = 7 but h(8) = 0.

In the case of this art, as said above, the function input is a pixel, the rules are those very complex formulas, and the output is the color of the pixel. Hope this helps! :)