The concept of macroeconomics, Macro mean as a whole while economics means the economy, macroeconomics means the study of the whole economy. In macroeconomics we can study the whole economies and their related answer to questions like why some countries have experienced in rapid growth while other countries stay mired in poverty? Why some countries have high rate of inflation while the other have stable rate of prices? Why some countries have a high level of per capita income while the other have low PCI? Why some countries have low level of unemployment and other have high rate of un employment? What the policies are used to reduce the level of unemployment and level of inflation and maintain the prosperity and achieve the good growth of the economy? So, macroeconomics studies the economy as a whole, and attempts to answer these related questions.
In everyday life we can see such as income growth, inflation rate, prices indexes, stock market up down, recession, recovery and depression of the economy, consumption pattern of economy, aggregate demand and supply, etc. etc. indicate the importance of the study of the macroeconomics.
Macroeconomics play an important and central role in political debates. Macroeconomics also study the world politics and their impact on the world trade balance of payment, imports and export. Macroeconomics also study financial policy, exchange rates. Real GDP, Inflation Rate, Unemployment rate are the key study of macroeconomics. Real GDP measure the total income of everyone in the economy. Inflation Rate measure the fraction of labor force out of work
Macroeconomics study how these variables are determined, why they are change over a period of time, and how these variables are interacting with each other.

Endogenous Variables are those variable that a model tries to explain.
Exogenous Variables are those that a model takes as given.