[Haskell-beginners] Handling a MonadError

[Christopher Howard]

Related question: Could you explain the typeclass definition for
MonadError to me?:

class (Monad m) => MonadError e m | m -> e where
    throwError :: e -> m a
    catchError :: m a -> (e -> m a) -> m a

More specifically: Why is there a pipe symbol followed by what looks
like a function definition in the "class" line? The typeclass
definitions from the tutorials I went through were simpler, like:

class BasicEq a where
    isEqual :: a -> a -> Bool

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