A merchant bank is historically a bank dealing in commercial loans and investment. In modern British usage it is the same as an investment bank. Merchant banks were the first modern banks and evolved from medieval merchants who traded in commodities, particularly cloth merchants. Historically, merchant banks' purpose was to facilitate and/or finance production and trade of commodities, hence the name "merchant". Few banks today restrict their activities to such a narrow scope.

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.