In theory, democracy is a government elected by the people, for the people. In practice, not so.

The term democracy is derived from the Greek dēmokratiā—meaning dēmos (“people”) and kratos (“rule”). It existed in limited form in 5th BC in some Greek city-states like Athens. The Roman called their government Republic but the participation was limited to nobles and big landowners. After the fall of Roman Empire, all kinds of governments came into existence: monarchy, dictatorship, oligarchy (rule of the few). For a long period, monarchy was popular, but it too did not last; only the British—the traders that they are–turned the monarchy into a tourist industry.
The representative democracy—each adult having one vote–is a modern phenomenon. The development of sea, land, and air transportation—result of constant technological innovations–led to constant trade expansion, and it, in turn, led to the spread of democracy. It is good to remember that democracy is more of an ideal than a reality. Winston Churchill called it the worst form of government, except for all the others.
The USA was the first country to deliberately choose democratic form of government in 1787. But initially, blacks, women, and Native Americans had no voting rights. The progress has come slowly. One reason why democracy is always a distant goal is that it does not fit human nature—as long as the powerful and the rich have what they want, they really don’t care much about others’ needs or  wants.  Also, they don’t care how they get power or money and how they hang on to it. The result is that the “have-nots” have to constantly fight the “haves.” Sometimes they succeed a little and sometimes it gets ugly. The point is that democracy is prone to all human weaknesses: exploitation, corruption, lies, hypocrisy, and lack of accountability, pretensions etc etc.

Democracies are as varied as the people and the nations: Presidential and parliamentary systems, central and federal systems, two-party and multi-party, different methods of election and so on. The structural differences lead to several problems: tyranny of the majority, lack of education, extreme poverty and extreme riches, lack of universal health care. Despite this, no one wants to switch to monarchy or dictatorship. It does satisfy the human desire to feel more or less free and somewhat equal. And then, there is some satisfaction in “nothing is perfect after all.”