Forex is an abbreviation for FOReign EXchange; the trading of currencies. Strictly speaking this isn't correct, in forex you are usually trading currency pairs. What that means is that you exchange one currency for another and later reverse that again. Because currency values vary you could 'buy low' and 'sell high' and thus making you some profit.

The forex market is by far the biggest market on earth! With a daily turnover of billions of dollars it is even a lot bigger than the stock markets. Traditionally the forex markets were only accessible for the rich and the banks but fortunately that has changes. Now even investors with accounts as little as $500 can access the forex markets. 

To be able to trade forex you will need a broker account. A broker is an intermediair that can provide you with the software to be able to trade on the forex markets.  Keep in mind thought that the forex markets are strictly regulated by financial authorities. To open up a forex account you will need to send in paperwork with copy of ID. 

One really good aspect of this setup is that you are always in complete control of your own money. Unlike with the investment programs where you hand over money to others and hope for the best. With forex, you are in control.

Typical for forex trading is the fact that trading is done with a 'leverage'. This is great for creating profits but it also means potential losses are leveraged.

Forex is not for the faint hearted! I found that the hardest thing about trading is ignoring emotions and stick to a strategy. That can be difficult if you see some losses in your account. If you're going to trade forex be sure to have a system (like FreedomRocks) and enough cash to play with. Do that, stick to the plan and you could be earning your own money online.

A small technical FAQ about forex trading can be found here.