CCD Cameras are very sensitive digital cameras. They are built around a Charge-Coupled Device (or CCD) that can detect photons (packets of light) falling into the millions of tiny buckets (or pixels) on its surface and then manipulate them so that they can be read, stored and used to reconstruct the image that the camera was looking at.
In other words, they can produce digital images. These digital images can then be transferred easily around the world using the Internet and processed using special astronomical data reduction software.
The electronic chips inside CCD cameras are very much like those in video cameras and small digital cameras. However, to make them more sensitive, they have to be kept very cold - usually below -100°C!
CCD cameras only measure the brightness of an object, not its colour, so special coloured filters are used to make simple measurements of the colours.