ICC profiles contain information that characterises a colour input or output device in accordance with standards set up by the International Colour Consortium (ICC).
Each ICC profile describes the colour attributes of a particular device by defining the most saturated colours the device can produce in a standard colour space. By having a standardised reference, colour reproduction can be controlled throughout an entire imaging workflow.
An ICC profile can be created for every device or medium that captures or displays colour. However, for digital photography, the most important devices to profile are the monitor and the printer because if they can’t communicate colours and tones correctly, what you see on the monitor will not look like the image when it is printed.
To profile a device you must map the way it reacts to a standard colour input. Once this information is known, the device can interact with other profiled devices to ensure the result of the interaction is as close a match to the known standard as possible. This means consistent colour reproduction across the entire imaging chain.