Forex indicators are extremely important when it comes to trading. The reason is because he cannot possibly be looking at every aspect of the market if you're just one person. However, you can program a machine to do that for you. A Forex indicator will simply look around at whatever aspect of the market you ask it to, and give you a live update of whatever has changed. You can use this to trade on by itself or you can use it in combination with other for its indicators.
There are essentially three kinds of Forex indicators. There are expert advisors, technical indicators, and fundamental indicators. Between these three, the easiest to read is an expert advisor. An expert advisor will scan technical and fundamental indicators for you and give you a trading recommendation based on those. You can follow this trading recommendation if you agree with that, or you can pass it up if you think that the market conditions are not right to use that indicator.
Technical indicators mean anything dealing with price. This can mean a change in the cost that is based on a moving average or based on a significant amount of buying or selling momentum. As long as it is some sort of a derivative of price movement, then it is considered to be a technical indicator. Technical indicators are a lot easier to read than fundamental indicators, but there are still more complex than expert advisors. The reason is because you still have to interpret them, and often there are several of them on your screen at a time.
Finally you have a fundamental indicator. Fundamental indicators are extremely complex to read because they are based purely on economic factors. These can be anything from an announcement that was made by the Federal Reserve Bank, or recent report of job losses. You typically cannot find a way to display a fundamental indicator on your trading platform, but you can still read them from other areas. There are a lot more difficult to interpret because fundamental indicators are a lot more subjective. However, there are still extremely useful and should be used in tandem with other similar technical indicators.