Simply put, forex is the trading of currency, buying low and selling high. There are some levels of risks involved as in all other risky dealings but the rewards can be very good indeed.
The stability of the forex is never guaranteed as it is dictated by many connective elements around the world. Things like war, oil prices, and global shifts in power are just a few of the elements that effect the forex movements. However most times these changes are not immediate but gradual over time.