To further explain, in most financial jargon, one often call an index by its (historically) most traded tracking fund. That is, the NASDAQ 100 is often called the QQQ, the S&P 500 is often called "spider" (SPDR), etc.
But you're 100% right, in a comment about vocabulary, jargon has no place.
QQQ is an index fund:
* https://en.wikipedia.org/wiki/Invesco_QQQ
That follows the Nasdaq-100 index:
* https://en.wikipedia.org/wiki/Nasdaq-100
There are other funds that track it too from companies other than Invesco.