Equities are synonymous with shares or stocks, and the terms are used interchangeably. When you invest in shares or stocks of a company, you are essentially buying an equity stake in it and becoming a part-owner of a given company. A company that registers itself on the stock exchange for trading offers its stocks or equities to the general public. Investors can choose the number of shares, and the subsequent investment amount, based on the shares available in the equity trading market.