I just found the symbol `ExpectationE` with autocomplete.

[![enter image description here][1]][1]

Rendered the symbol is

[![enter image description here][2]][2]

Searching the documentation and the internet leads to nothing. Does somebody know what this symbol does and what its purpose is?


  [1]: https://i.sstatic.net/LwYXE.png
  [2]: https://i.sstatic.net/jTdWK.png