Apple has announced an event that will stream on September 14, 2021 at 10 a.m. PDT. You can view the online event at Apple.com or on the Apple TV app.
No official products have been announced. There is speculation that Apple may announce iPhone 13, Apple Watch 7, new AirPods, or other hardware including iPad Mini.
It does not appear likely that iOS 15 or Monterey, the latest MacOS will be released on this date. But, as with most Apple events, you will likely not know until you know.
You can learn more here.