Can anyone simplify this gst related statement for me. ?

I was reading about "Who is Liable to get Registered under GST? "   and there was a point  that reads as

"Person supplying online information and database access or retrieval services from a place outside India to a person in India, other than a registered taxable person"

I wonder why a person staying outside india and giving service to a person in India , need to register for GST, because he is not a citizen ..?

Or may be i don;t fully understand the para,  so can someone simplify this for me. ?

Thanks & Regards