Intermediaries who bring the buyer and sellers of financial products together. For this service, they charge a fee called commission.
Products typically are stocks, bonds, and options.
This is one of the attributes which makes the existing investment system centralized. Accounts that are set up with these entities turn them into custodians.
Decentralized Finance (DeFi) seeks to alter this by not requiring anyone to act as a custodian for the assets. Through the use of peer-to-peer (P2P) technology, buyers and sellers are brought together. In fact, with the introduction of liquidity pools, there is not need for both parties. The pool serves as a built in buyer or seller, depending upon what the individual engaging with it wants to do.
If this takes place, Brokerage Firms could see a reduction in their business as they lose control of investors. With the existing system, they entrenched themselves as gatekeepers.