Forex signals are forecasts of forex trading points from expert traders on the market, they predict the changes of a pair rate, they can see if it will go up or down and how much it will change.

For an example.

Forex automony is a forex signal provider that will try to give you 80% accurate signals, with this signals you can calculate the stop lose and take profit parameters.

They provide three types of forex signals

1. Intraday signals, short signals that will happen in short period of time (hourly), those signals are the most profitable because you can make multiple small profits that will sum up at the end of the day with good profit.

2. Daily signals, that will give you the changes of each currency pairs at the end of each trading day. With knowing this parameters you can learn the direction of the charts, although the chart will go up and down, but eventually in 80% accuracy it will behave as they expected. Knowing this could help you make better decisions on the intraday trading deals.

3. Weekly signals are for long term deals, here are the most profitable and risky at the same time deals. Knowing the long term changes could help you make huge profits from one deal.

There are no 100% accurate signals, because those signals are predictions of experts traders and, those experts make these prediction by taking all factors and elements in account, but we all know the sometimes small changes in the market, an announcement, or even politic incident can change everything in the forex market. 

But in general those signals are much better than nothing, and it's like getting direct help and opinion from trading experts.

I can recommend only two forex signals providers but I will not review them, I found them as the most accurate in the market. 

http://www.arabian-affiliate.com/forex/forexsignals.htm