title: What is the meaning of the Haskell operator "<>"?
body: <p>In Haskell, what is the meaning of the <code>&lt;&gt;</code> operator (as distinct from <code>&lt;*&gt;</code> or <code>&lt;$&gt;</code>). I am seeing references to it while researching <a href="https://hackage.haskell.org/package/optparse-applicative" rel="noreferrer">the optparse-applicative package</a>. Neither Google nor LYAH seem to have any information.</p>