I've been adviced to think Ing form as Timeless and It implies the meaning in a sentence depending on the context.
I have read in The forms of the gerund (Grammaring) as follows:
The simple gerund can refer to the same time as that of the verb in the main clause
The simple gerund can also refer to a time before that of the verb in the main clause
So, I've found two sentences which are the words from @stoneyB. In his answer:
Could you tell which form of ing form it is in these sentences(I think they are in passive simple gerund) :
The minister underwent the experience of eggs being thrown at him.
You have undergone the experience of its being explained.
It seems in both of these sentences, the passive gerund being+past participle is present, Isn't it ? But what about the time reference that "ing form" refers to here in these sentences, to the same time as the main verb, before the main verb or what Implication or meaning the ing-form here refers to ?