What's the difference?

You are asking for a non-trivial amount of work here. Perhaps this is a case where you could do some basic reading on the topic, then come back with some more specific questions.

-john-

Investment banks *originate* (ie. create) stocks and bonds for the issuers (the companies which go public via sale of stock or borrow money on the public markets by issueing bonds). They sometimes hold on to some of those issues in their own portfolios and trade for their own profits, but their main job is creating these securities.

Mutual funds are pools of investor's money which is used to buy these investments. They are generally open to the public to buy up and participate, and they are regulated somewhat strictly (compared to those below). The mechanics of how this work is way beyond the scope of this quick e-mail. (see also "closed-end funds" and "Exchange-traded funds" or ETFs).

Hedge funds are similar but they are far less regulated and they are not open to the public to participate in. Hedge funds may invest in almost anything and may borrow money, sell things short, and invest in illiquid assets. They have limits on the number of folks who may invest in them, and those folks generally have to be institutional investors or very wealthy.

Private equity groups also pool "sophisticated" investors money (like hedge funds) but they are generally of a more specialized purpose - they buy up entire companies rather than stock that trades on exchanges. Sometimes they borrow huge heaps of money to buy up enough of an existing public company to take it private - ie. to buy the whole thing up. Sometimes they just buy parts of other companies up.

Most regular individuals have nothing directly to do with investment banks (they buy funds or if they buy individual stocks, it's usually on the secondary market, not at issuance). And they have nothing at all to do with hedge funds or private equity.

If you have a specific question, go ahead. But I'd suggest doing a little reading first. I like Eric Tyson's For Dummies books a lot - see his books Personal Finance for Dummies and Investing For Dummies. The names of the books may be a little insulting, but the content is very good and very easy reading.