<p>According to <a href="https://arxiv.org/ftp/arxiv/papers/1803/1803.10195.pdf" rel="nofollow noreferrer">What we talk about when we talk about monads</a> the question &quot;What is a monad&quot; is wrong:</p>
<blockquote>
<p>The short answer to the question &quot;What is a monad?&quot; is that it is a monoid in the category of endofunctors or that it is a generic data type equipped with two operations that satisfy certain laws. This is correct, but it does not reveal an important bigger picture. This is because the question is wrong. In this paper, we aim to answer the right question, which is &quot;What do authors really say when they talk about monads?&quot;</p>
</blockquote>
<p>While that paper does not directly answer what a monad is it helps understanding what people with different backgrounds mean when they talk about monads and why.</p>
What is a monad?
<p>Having briefly looked at Haskell recently, what would be a <em>brief, succinct, practical</em> explanation as to what a monad essentially is?</p>

<p>I have found most explanations I've come across to be fairly inaccessible and lacking in practical detail.</p>