What is difference between macro and micro economics ?

Macro economics is study of consumption and production activities with averages and aggregates of the system. It study the forces that effect economy as whole while assuming that all economics units are homogenous. Macro economy is top-down view of economy while micro economics is bottom-up view of economics. It studies problems and policies given at particular time and place. It fails to explain how overall economy works.

Economic Model : Highly simplified representation of real world. Un-necessary irrelevant information is removed from model to make is simple and sometimes approximation and assumption are done. the process of removing un-necessary information is known as "Ockham's Razor".