Hedge Fund
The main characteristic of a hedge fund is its extreme lack of oversight. Rather than being regulated and overseen by a major securities administrator, hedge funds are given free rein to invest as they see fit. Some of the only restrictions in place have to do with who is permitted to invest in a fund.
So-called “qualified” or accredited investors may participate. For individuals, this typically means someone with over $1 million in net worth or at least $200,000 annual income ($300,000 if married). More often, those investing in hedge funds are themselves other investment funds: pension funds, so-called funds of funds, trusts with assets over $5,000,000, etc.
Outside restricting who can participate, hedge funds are distinct in terms of the freedoms they have. They can invest in just about anything, and take short positions as well as long (in other words, betting that the market will fall rather than rise) in the stock market.