Unification- It is a trial to correlate and unite various universal laws and basic phenomena of nature to explain an activity.

Eg. Maxwell unified electric, magnetic and optical phenomenon on when he explained that light is an electromagnetic wave.

Reduction - it is breaking down of a complex system in to simple constituent systems  to so that laws of physics can be applied on these systems and we can understand the working of the complex system.

Eg. A complex sound can be broken down to simple sine waves. so that we can make the sound-piece from the simple tones.