title: In pandas, what is the difference between [list] and [[list]]?
body: <p>I'm sorry if this question is already answered, but I truly don't know the different names of either of those (object or list or array?), so I am still confused.</p>
  <p>I'm just curious as a follow up from this question.</p>
  <p><a href="https://stackoverflow.com/questions/59879577/pandas-getting-typeerror-only-integer-scalar-arrays-can-be-converted-to-a-sca">Pandas: Getting &quot;TypeError: only integer scalar arrays can be converted to a scalar index&quot; while trying to merge data frames</a></p>
  <p>And the answer by <a href="https://stackoverflow.com/a/59906739/5143122">Ilyas</a>.</p>
  <p>Why <code>[[list]]</code> resulted in an error</p>
  <blockquote>
  <p>only integer scalar arrays can be converted to a scalar index</p>
  </blockquote>
  <p>but <code>[list]</code> doesn't?</p>