A feeder fund is a legal entity that pools capital from investors and then invests the pooled capital in an affiliated master fund. The master fund is the legal entity that actually makes investments in stocks, bonds, cryptocurrency, real estate, and other alternative investments.
A hedge fund is an organization which most commonly uses the master-feeder fund structure; however, the structure is also used by private equity funds, venture capital, and other investment management companies. Most master-feeder fund structures will have one or two feeder funds, but some structures can have many more.
For a sample feeder structure, see our page on master-feeder hedge fund structures.