QFuture::then() documentation about threading is unclear

The docs for QFuture::then() say https://doc.qt.io/qt-6/qfuture.html#then :

Attaches a continuation to this future, allowing to chain multiple asynchronous computations if desired. When the asynchronous computation represented by this future finishes, function will be invoked in the same thread in which this future has been running. If the continuation is attached after the parent has already finished, it will be invoked in the thread where the parent lives. This method returns a new QFuture representing the result of the continuation.

I'm not sure what "this future has been running". A future does not run on any thread. Does it mean "on the same thread that fulfills the promise associated to this future"?

Similarly: in "parent has already finished, it will be invoked in the thread where the parent lives", what is meant by "parent" here?