Summary
It takes several steps for a digital camera to take a picture. Here's a review of what happens in a CCD camera, from beginning to end:

You aim the camera at the subject and adjust the optical zoom to get closer or farther away.
You press lightly on the shutter release.
The camera automatically focuses on the subject and takes a reading of the available light.
The camera sets the aperture and shutter speed for optimal exposure.
You press the shutter release all the way.
The camera resets the CCD and exposes it to the light, building up an electrical charge, until the shutter closes.
The ADC measures the charge and creates a digital signal that represents the values of the charge at each pixel.
A processor interpolates the data from the different pixels to create natural color. On many cameras, it is possible to see the output on the LCD at this stage.
A processor may perform a preset level of compression on the data.
The information is stored in some form of memory device (probably a Flash memory card).

A memory stick