I've been hearing this sentence structure for a while, so i wanted to learn about it but couldn't find specific information on the internet since i didn't know how this structure was named in English grammar.
For example there are lots of people that you don't like in a party and you are unhappy about this. It's possible to say:
I'm unhappy about their presence.
I'm unhappy that they are here.
But you can also say:
I'm unhappy about them being here.
So it goes like: [main clause + (about) + object + -ing form]
Is there a specific name which has been given to this structure? And what are the properties of this structure in general?