HCI Vs SAP PI

Dear All,

I read many articles on internet about HCI( Hana Cloud Integration) which contains all PI capabilities and integrate cloud to on premises, cloud to cloud,....etc

And PI is also option to integrate Cloud to on premises , cloud to cloud.

But I am still confusing on that, PI on-premises server is possible to integrate cloud to cloud  and cloud to On-premises? if possible how?

Thanks & Regards,
Sateesh