[Haskell-cafe] Why does Haskell have both `Maybe a` and `Either a ()`?

Greetings, everyone! Recently I was involved in a discussion on the new ML-style language 'gleam'. Gleam has for quite a while now only had an `Either a b` type, with all functions that in Haskell one would use a `Maybe a` for, working on an `Either a ()` instead. In the discussion(https://github.com/gleam-lang/gleam/issues/591), the language designers were asking the community whether it would make sense to add `Maybe` to the language as well, or keep using only `Either a ()`. My question: Is the difference between `Maybe a` and `Either a ()` only semantic and are they functionally equivalent, or are there differences in functionality as well? Have a nice day, ~Marten / Qqwy