Let's say I want to buy stocks of Sinopec which is a Chinese company. I would expect to buy it from HKS and in local currency. With the Degiro broker which is Dutch, I see "Sinopec Shangai Petrochem-H in the search in HKS but I cannot buy it; there is no price. Instead of that I can buy another one in NSY "Sinopec Shangai Ads" in US dollars. I can also see other "versions" of the company in the German stock exchange. Can someone explain to me what is happening? If I buy the one from NSY, is it the "real" Sinopec?