Detection, classification, recognition and identification is all very easy until you put it in practice. Then you realize that there are big practical and subjective problems that make using them difficult.
Academically, the terms are straightforward and reflect what they mean in real English:
Detection - The ability to detect if there is some 'thing' vs nothing.
Recognition - The ability to recognize what type of thing it is (person, animal, car, etc.)
Identification - The ability to identify a specific individual from other people
Obviously, each level is harder and requires more detail, going from detection to recognition to identification.