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CCD and CMOS are two commonly used sensor in the imaging world. Both has their pros and cons. Depending on their use in a particular field manufactures decide which they will use in their intended device.
CCD (Charge Coupled Device) was invented back in 1969 for the movement of electrical charge, usually from within the device to an area where the charge can be converted into a digital value. This is achieved by “shifting” the signals between stages within the device one at a time. CCDs move charge between capacitive bins in the device, with the shift allowing for the transfer of charge between bins.
CCD image sensors are widely used in professional, medical, and scientific applications where high-quality image data is required. In applications with less exacting quality demands, such as consumer and professional digital cameras, CMOS are generally used.
CMOS is an alternative to CCD image sensor. They are most commonly used in cell phone cameras, web cameras and in most DSLRs. The biggest advantage of a CMOS sensor is that it is typically less expensive than a CCD sensor.
Since a CMOS video sensor typically captures a row at a time it may result in a “rolling shutter effect” (image is tilted to the left or right, depending on the direction of camera or subject movement). For example, when tracking a car moving at high speed, the car will not be distorted but the background will appear to be tilted. CCD sensor does not have this problem. CCDs are also preferred in astronomical devices. (Source : WiKi)
Below is an animation from Nokia How an imaging sensor captures an image.
The following animations created by Raymond Sirí nicely demonstrate the method CMOS and CCD sensors use to transfer digital signal.
CMOS Animation Sequence
CCD Animation Sequence