Satellites use a camera to take pictures. A radar transmits an electronic signal that bounces off objects and returns for analysis. Both systems can detect stationary or moving objects, but the display presented on a viewing screen can differ immensely. Satellite cameras can show images as they actually appear, but radar can create representations to show things the camera may not reveal.
Satellites can carry many sorts of digital still and video cameras that send signals back to Earth for thousands of applications. They can use different lens and filters to pierce through certain types of weather obstructions and can focus on single small object or wide areas. Weather satellites can take pictures of an entire hurricane several miles wide. A surveillance camera can monitor the activities of people or vehicles or photograph documents to such accurate detail that the operator can read them.