Red Chips: Shares of companies incorporated in Hong Kong that trade on its exchange and are quoted in Hong Kong dollars. Most of the firm's operating assets and sales are in Mainland China, and 30% or more of its shares are held by Mainland Chinese entities (government or individuals).
H Shares: Issued by companies incorporated in China; they trade on the Hong Kong exchange in Hong Kong dollars or other currencies. ("H" stands for Hong Kong.)
A Shares: Issued by Chinese companies and denominated in renminbi. They are sold on the Shanghai and Shenzhen exchanges almost exclusively to domestic investors.