投资公司专门从事投资、再投资及买卖证券业务的公司。这种公司通过发行股票和债券，将小额投资人的资金汇集起来按规定的目标进行再投资，从而为投资人提供更多的投资多样性、流动性和专业管理服务。它与控股公司〔holding company〕不同，后者寻求对被投资企业进行控制，而投资公司只为自己营利进行投资而且其所从事的投资通常也是多样化的。投资公司通常有两种：
１开放型〔open-end〕，如常见的互助基金〔mutual fund〕。这种公司不上市，股份数额不固定，可以根据需求随时向投资人出售新股份或回购旧股；
２封闭型〔closed-end〕，亦称作投资信托公司。这种投资公司的股份是固定的，股票上市交易。
广义投资公司，是指汇集众多资金并依据投资目标进行合理组合的一种企业组织。既包括信托投资公司、财务公司、投资银行、基金公司、商业银行和保险公司的投资部门等金融机构，也包括涉足产权投资和证券投资的各类企业。其业务范围包括购买企业的股票和债券、参加企业的创建和经营活动、提供中长期贷款、经营本国及外国政府债券、基金管理等，资金来源主要是发行自己的债券、股票或基金单位，从其他银行取得贷款，接受委托存款等。狭义的投资公司，则专指公司型投资基金的主体，这是依法组成的以营利为目的的股份有限公司，投资者经由购买公司股份成为股东，由股东大会选定某一投资管理公司来管理该公司的资产。
Investment company is a company that specializes in investing, reinvesting, and buying and selling securities. By issuing stocks and bonds, this kind of company can pool the funds of small investors and reinvest them according to specified targets, so as to provide investors with more investment diversity, liquidity and professional management services. It differs from a holding company, which seeks control of the investee enterprise, which invests only for its own profit and usually in a variety of investments. There are usually two kinds of investment companies:
1. Open-end, such as the common mutual fund. This kind of company is not listed, the amount of shares is not fixed, and can sell new shares or buy back old shares to investors at any time according to demand;
2. Closed-end, also known as investment trust company. Shares in such investment companies are fixed, and shares are traded on the stock market.
Generalized investment company, refers to the collection of a large number of funds and according to the i
nvestment objectives of a reasonable combination of enterprise organization. It includes financial institutions such as trust and investment companies, finance companies, investment banks, fund companies, commercial banks and the investment departments of insurance companies, as well as various enterprises involved in equity investment and securities investment. Its business scope includes buying stocks and bonds of enterprises, participating in the establishment and operation of enterprises, providing medium - and long-term loans, dealing in domestic and foreign government bonds, fund management, etc. The main sources of funds are issuing its own bonds, stocks or fund units, obtaining loans from other banks, and accepting entrusted deposits. In the narrow sense, investment company refers to the main body of corporate investment fund, which is a profit-making limited company formed according to law. Investors become shareholders by purchasing shares of the company, and the shareholders' meeting selects an investment management company to manage the assets of the company.