Although we hear the word "radar" a lot in everyday life -- when the weather anchor says that the Doppler radar indicates it's going to rain, for instance -- it might seem relegated to pretty specialized roles.
Radar uses electromagnetic waves to measure distance and detect velocity and location, and it turns out we have to measure and detect those things a lot. The airline industry is using radar, of course, to identify aircraft or warn of an approaching hazard. But did you know the military is also using radar to detect landmines in former war-torn countries? Or that they're also starting to employ radar to identify bombs and suicide bombers? Using a radar gun, waves are shot to and bounced back off a person. There's a large database of "normal" signals given off by people; if there's an "abnormal" reading from the radar, alarms go off and that backpack is going to be searched.
Ok, that stuff is cool but you're probably not using it. But if you eat fish, chances are you're reaping the benefits of radar (and it's sound wave cousin, sonar). Industrial and even recreational fishing boats use radar to detect schools of fish, saving them time and money searching for the big catch. Radar is also being used around you if you're in an earthquake or volcano zone. Geologists rely on it to detect changes in the Earth's layers, which could provide an early warning system for a natural disaster.