title: What is an element in Flutter?
body: <p>I'm having a hard time understanding what an element is in Flutter.  From the doc:  "An instantiation of a Widget at a particular location in the tree".
  . . . I guess now I have to ask, what is the tree.</p>
  
  <p>At first, I thought the tree referred to the states of widgets, but StatelessWidget also has createElement, so this doesn't seem the case.  Then, I thought that the tree referred to the parent/child relationship, but it is not clear to me.  Finally, it sounds like an element is sort of like a snapshot of the widget at that particular time and location, but the associated methods don't seem to reflect that.  Am I anywhere close?</p>