What is understood by unification and reduction in physics?

Unification: It is a trial to correlate and unite various universal laws and basic phenomena of nature to explain an activity. For example—Maxwell unified electric, magnetic and optical phenomenon on when he explained that light is an electromagnetic wave.
Reduction: It is the effort to solve a complex problem by breaking it into simpler parts. It is considered to be heart of physics. For example temperature of a system is reduced to average kinetic.