The MaybeT transformer is defined as:

newtype MaybeT m a = MaybeT {runMaybeT :: m (Maybe a)}

 
instance Functor m => Functor (MaybeT m) where

  fmap f x = MaybeT $ fmap (fmap f) $ runMaybeT x


....

Question:  What does "runMaybeT x" mean?


Thanks,

Daryoush