[Haskell-beginners] applicative default structure

This code is using Applicative Maybe. The structure is provided by Maybe and the value 1 is wrapped in this structure. No surprises here. Prelude> pure 1 :: Maybe Int Just 1 Prelude> :t (pure 1 :: Maybe Int) (pure 1 :: Maybe Int) :: Maybe Int ...but can somebody explain the type of x below? Prelude> x = pure 1 Prelude> x 1 Prelude> :t x x :: (Applicative f, Num a) => f a What is f here? Thanks!