A-shares, or ordinary RMB stocks, refer to ordinary stocks registered and listed in mainland China. A-shares are issued by companies in mainland China and are available for domestic institutions, organizations or individuals (only customers with Chinese ID cards) to subscribe and trade in RMB. A-shares are also traded on the Shanghai Stock Exchange (SSE) and the Shenzhen Stock Exchange (SZSE).

Listed A-share companies mainly include the following categories:

1. Main Board: Commonly known as the Shanghai-Shenzhen Main Board, it refers to stocks listed on the main board market of the Shanghai Stock Exchange and the Shenzhen Stock Exchange. These stocks generally come from large, mature and profitable companies.

2. GEM: Also known as the second board market, it is a platform for financing and development for small and medium-sized enterprises and innovative start-up companies with high growth potential. The stock code of the GEM starts with "300" and is mainly listed on the Shenzhen Stock Exchange.

3. Science and Technology Innovation Board: The Science and Technology Innovation Board is a platform in the capital market of mainland China that specifically provides financing and development for technology innovation companies. The stock code of the Science and Technology Innovation Board starts with "688" and is mainly listed on the Shanghai Stock Exchange.

4. NEEQ: The full name is "National Equities Exchange and Quotations for Small and Medium Enterprises", which is a platform for equity trading for small and medium-sized enterprises. NEEQ stocks start with "400", "83" or "87" and are mainly listed on the Beijing Stock Exchange.

It should be noted that A shares are not stocks of all mainland Chinese companies. For example, large companies such as Alibaba and Tencent choose to list on the Hong Kong Stock Exchange or other overseas exchanges. Therefore, A shares are mainly a microcosm of stocks of companies in mainland China.