The term "politics" derives from the Greek word "polis", meaning city-state. It refers to the way in which human beings interact in large groups to organize their society. The term can also refer to that study of how to govern and the ways people engage in debates and power struggles over collective decisions.
Government refers to the actual structures of rulership, power, and control in a society. In other words, people engage in political struggles to form governments. Once in place, governments are entities that enact and enforce laws and otherwise organize groups of people to work together collectively.
Governments are classified by the nature of how power is allocated and wielded, with power in monarchies being wielded by a single person, in oligarchies by a small group, and in democracies by all adult citizens.
In republics, rather than citizens being directly involved in the legislative process, citizens elect representatives (i.e. a Congress or Parliament) who then form a government and legislate.