A CCD is an image sensor that moves each pixel’s charge across the chip to a single output, which gives a uniform response and low noise. It was the standard security camera sensor before CMOS became dominant, and some low-light models still use it. The two differ in how they read an image, not in what they can see.
Sensor choice explains why some cameras look grainy at night and others do not. CCD and CMOS handle charge differently, and the difference shows up in low light.
How a CCD reads an image
Light generates charge at each pixel, and the chip passes that charge row by row to one amplifier at the corner. A single output path treats every pixel the same way, which helps consistency. The trade is power and speed, because the charge has to travel across the chip.
CCD and CMOS in practice
A CMOS sensor converts charge to a voltage at each pixel and reads them in parallel, which is faster and less costly to produce, and it now dominates the market. CCD sensors remain in some specialized low-light cameras. For a buyer, the sensor type matters less than measured low-light performance.