Radar detectors are devices that can be used to detect the presence of radars before you reach them, so you can avoid getting a speeding ticket from the police. There are even models that can detect the presence of laser guns, so they are even more effective than standard radar detectors.
A bit of info on radio waves
A radar works based on radio waves that bounce back between the radar and a moving car. Based on how fast this happens, the radar can tell the movement speed of the car, and this is how the police can tell if you were going over the speed limit. Such aspects are important to understand, so you can understand how radar detectors work.
What radar detectors do is that they can detect the radio wave emitted by the radars in its path, some time before you get in their range with your vehicle. They simply tell you when it is the right time to lower your speed, so you do not get a speeding ticket.
What more advanced models can do?
While most radar detectors do what just was said earlier, there are more advanced models that can even emit a scrambled signal so they can throw off the readings of the radar. This means that you can speed up while going by a radar and still not get caught, but it is a dangerous technique and not so advisable.
Different types of radar detectors
You can now get all kinds of radar detectors, each one with its own set of characteristics. Some can detect a radar from miles away, others have a small wavelength and so on.
No matter what kind of detector you want to get ( but you should definetely search for the best radar detector for your budget), remember that driving at a legal speed is recommended because it can save your life in case of a traffic accident.