What is a Forex Account?

A Forex account is an account used to hold and trade foreign currencies. Typically, you open an account, deposit money denominated in your home country currency, and you can buy and sell pairs at will.
The purpose of this, is to hopefully profit from fluctuations in currency values. You would want to try to match up a currency that is appreciating in the value, against one that is decreasing in value. You buy or sell the pair and hold until you think the rise or fall of the pair is over.