You want to use CCTV for a variety of reasons:
Around the home, just the sight of a camera on a property alerts the would-be thief that this home will not be a push-over.
CCTV can even be installed in your cars! You see this in some of the newer cars as a camera used in backing up.
Commercially, in banks and stores, CCTV is used in stores to inhibit theft. They are also being used commercially to assist in the observation of people working with dangerous machinery.