QDII

A qualified domestic institutional investor or QDII is an institutional investor that has met certain qualifications to invest in securities outside of their home country. QDII programs started in China in 2006 and allow five types of Chinese entities to invest abroad: insurance companies, banks, trust companies, funds, and securities firms. Entities that want to participate in the QDII program must first receive approval from China's State Administration of Foreign Exchange (SAFE), which is also responsible for establishing the investment quota amount allowed each participant. Once approved, entities are allowed to make investments in the overseas markets for both themselves or on behalf of retail clients. Firms can make investments in equities, fixed income, and derivatives in specified overseas markets.

合格境内机构投资者（QDII）是指取得相关部门批准或许可开展境外证券等投资的境内机构，包括但不限于：商业银行、证券公司、基金管理公司、保险机构、信托公司等。合格境内机构投资者可以自有资金或募集境内机构和个人资金，投资于法规及相关部门允许的境外市场及产品（银行自用资金境外运用除外）。我国于2006年实施QDII制度，由证监会等行业主管部门负责资格准入审批，国家外汇管理局负责对QDII机构的投资额度、资金账户、资金收付及汇兑等实施监督、管理和检查。这一制度让国内投资者直接参与国外市场，有利于继续扩大对外开放。

QFII

The Qualified Foreign Institutional Investor (QFII) is a program that allows specified licensed international investors to participate in mainland China's stock exchanges. The Qualified Foreign Institutional Investor program was introduced by the People's Republic of China in 2002 to provide foreign institutional investors with the right to trade on stock exchanges in Shanghai and Shenzhen. Before the launch of the QFII program, investors from other nations were not allowed to buy or sell stocks on Chinese exchanges due to the country’s tight capital controls.

合格境外机构投资者（QFII）是指经中国证监会批准，使用来自境外的资金进行境内证券期货投资的境外机构投资者，包括境外基金管理公司、商业银行、保险公司、证券公司、期货公司、信托公司、政府投资机构、主权基金、养老基金、慈善基金、捐赠基金、国际组织等中国证监会认可的机构。我国于2002年实施QFII制度，由证监会、人民银行依法对合格境外投资者的境内证券期货投资实施监督管理，人民银行、国家外汇管理局依法对合格境外投资者境内银行账户、资金汇兑等实施监督管理。2019年9月，国家外汇管理局宣布，经国务院批准，决定取消QFII投资额度限制。

RQFII

In Dec. 2011, the CSRC started the Renminbi Qualified Foreign Institutional Investor (RQFII) program. Similar to the QFII program, the RQFII program allows foreign investors the opportunity to invest in China's stock exchanges. There are differences between the RQFII program and the QFII program, most of which have to do with easing restrictions on investors that made accessing the QFII program difficult.

为扩大人民币跨境使用，推进我国资本市场开放，2011年12月中国证监会推出人民币合格境外机构投资者（RQFII）制度，允许符合条件的境外机构在批准的额度内，运用来自境外的人民币资金投资境内证券市场。2019年9月，国家外汇管理局宣布，经国务院批准，决定取消RQFII投资额度限制；同时，RQFII试点国家和地区限制也一并取消。二者最明显的区别在于汇入境内资金的货币不同：QFII需要把外汇资金兑换为人民币进行投资，RQFII可以直接使用外汇资金进行投资。但是，2020年5月，中国人民银行、国家外汇管理局发布的《境外机构投资者境内证券期货投资资金管理规定》明确表示，合格投资者（包括QFII和RQFII）可自主选择汇入币种开展境内证券期货投资。

参考：

1. Investopedia

2. 百度百科

3.《合格境内机构投资者境外证券投资外汇管理规定》

4.《合格境外机构投资者和人民币合格境外机构投资者境内证券期货投资管理规定》