The Glass–Steagall legislation describes four provisions of the United States Banking Act of 1933 separating commercial and investment banking. The article 1933 Banking Act describes the entire law, including the legislative history of the provisions covered.

Investment banking pertains to certain activities of a financial services company or a corporate division that engages in providing advisory-based services on financial transactions for clients, such as institutional investors, corporations, and governments. Traditionally associated with corporate finance, such a bank might assist in raising financial capital by underwriting or acting as the client's agent in the issuance of debt or equity securities. An investment bank may also assist companies involved in mergers and acquisitions (M&A) and provide ancillary services such as market making, trading of derivatives and equity securities, FICC services or research. Most investment banks maintain prime brokerage and asset management departments in conjunction with their investment research businesses. As an industry, it is broken up into the Bulge Bracket, Middle Market, and boutique market.