The main board refers to the Shanghai and Shenzhen main boards, the first board market. The stock codes of the main board companies listed on the Shanghai Stock Exchange start with 600, and the stock codes of the main board companies listed on the Shenzhen Stock Exchange start with 000.

The small and medium-sized board is part of the main board market. It is a separate section of the main board market of the Shenzhen Stock Exchange. The issuance scale is smaller than the main board. All companies are listed on the Shenzhen Stock Exchange and it is also a first-board market; the stock code starts with 002.

The GEM is a second-board market and is an exclusive sector of the Shenzhen Stock Exchange. Compared with the main board and the small and medium-sized board, the growth of enterprises is more valued. The stock code starts with 300.

The New Third Board refers to the national small and medium-sized enterprise share transfer market, which provides a place for equity transactions for small, medium and micro enterprises that have not yet been listed. The entry threshold is low and the quality of enterprises is uneven.

Generally speaking, the main board is on the Shanghai and Shenzhen stock exchanges, while the small and medium-sized board and GEM are only on the Shenzhen Stock Exchange. All companies are listed companies and their stocks can be traded publicly. The New Third Board is a national trading market for small and medium-sized enterprises and is an over-the-counter market.

Markets, unlisted companies, have specific conditions for buying and selling stocks.

Extended information: Investor groups 1. Main board, small and medium-sized board and GEM: Except for those who are prohibited from buying and selling stocks by law, other adults can buy and sell stocks by opening a securities account in a securities company, and there is no minimum capital requirement.

The following people are prohibited from buying and selling stocks by law: employees of stock exchanges, securities companies and securities registration and clearing institutions, staff of securities regulatory agencies, and other persons prohibited from participating in stock transactions by laws and administrative regulations.

, shall not hold, buy or sell stocks directly or under a pseudonym or in the name of others, nor may they accept stocks donated by others.

?2. New Third Board: Institutional investors need to meet the following conditions: Legal person institutions with a total paid-in capital or paid-in share capital of more than 5 million yuan, and natural person investors in partnerships with a total paid-in capital contribution of more than 5 million yuan need to meet the following conditions:

The average daily financial assets in the investor's name in the last 10 transfer days are more than RMB 5 million, and he or she has more than 2 years of work or investment experience in the financial industry.