how does list comprehension work in haskell code example

Example: list comprehension haskell

list = [1, 2, 3, 4]

evens = [x | x <- list, even x] -- [2, 4]

mul3List = [3*x | x <- list] -- [3, 6, 9, 12]
odds     = [3*x | x <- mul3List, odd (3*x)] -- [3, 9]

allCombinations = [(y, x) | x <- list, y <- list] -- [(1, 1), (1, 2) ...