[Haskell-beginners] What is operator :| ?

[John M. Dlugosz]

On 3/28/2014 1:41 AM, Tony Morris wrote:
> It is the constructor for a non-empty list (Data.List.NonEmpty).
>
> http://hackage.haskell.org/package/semigroups-0.12.2/docs/Data-List-NonEmpty.html
>

Interesting— this is the page I had found: http://www.haskell.org/haskellwiki/Non-empty_list


So why do we need both :| and <| (or cons) ?