The term "hedge fund" doesn't really mean anything anymore. It's just an actively managed portfolio with a lower AUM on average than a mutual fund, the legal option to take on more risk, and a certain fee structure. There are a few main investing "disciplines" or "strategies" [1] that each fund manager tends to subscribe to, but it's impossible to talk about them intelligently as a group as they all make wildly diverse bets on different assets across the globe.

[1] See figure 3: https://wealth.barclays.com/wealth-management/en_us/home/tho...