Think of any wrapped context in Haskell (like Maybe ) as a sealed plastic Lego storage box:

Data (like the number 5) is a red Lego block inside.

A Pure Function is an instruction sheet ("Attach a blue block").

Pure Function

No Lego boxes here—just instructions applied to raw blocks sitting on desk.

It only looks at the inputs explicitly passed. No database calls, no reading system clocks, no side effects. The same input always yields the exact same output.

addOne :: Int -> Int addOne x = x + 1

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Functor ( fmap / <$> )

Got some building instructions, but the Lego block is locked inside a sealed plastic box.

A Functor acts like a pair of reach-in gloves: it applies the instructions to the wrapped block without breaking the box.

fmap ( + 1 ) ( Just 5 ) -- Returns Just 6

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Applicative (<*>)

What if both instructions AND Lego blocks are sealed in separate plastic boxes?

An Applicative opens both boxes, applies the…