Also, Processing is that language which emphasizes on feasibility for programmers to create software prototypes very quickly, to try out a new idea or see if something works. For this reason, Processing (and p5.js) programs are generally referred to as “sketches.”
setup(): It is the statements in the setup() function. It executes once when the program begins. createCanvas must be the first statement.
draw(): The statements in the draw() are executed until the program is stopped. Each statement is executed in sequence and after the last line is read, the first line is executed again.
Reference: 1. https://p5js.org/