What it is: 'Democracy' is usually understood to mean what America's president Abraham Lincoln described in 1863: 'government of the people, by the people, and for the people'.
What it means: There have since been many governments that have called themselves democracies but scarcely fit that description. It is usually agreed that the test of a democracy is whether any government in power can be voted out, peacefully, by a majority of the people (and using a fair and open voting system). The principles of democracy are such things as equality and justice, and it is true that these are desirable aims. But there are problems to think about. For example, a majority isn't necessarily right, and so may not choose suitable leaders. People can be persuaded, tricked or pressured by skilful political campaigns. It may be that sometimes only a minority of the people are wise enough to see what is best for a country. Any government is only 'for the people' if it genuinely seeks the best for them, rather than just appearing to do so in order to get voted into power. Once in power, even well-intentioned leaders may make decisions which are not in the people's interest or do not represent the people's views. (Freedom of speech doesn't guarantee that anyone is listening.) There are also arguments about what kinds of voting system are really democratic. As for war, it is rare even in democracies that the people are in control of the country's military power, its intelligence information, and the decisions to use these against another country.
Think about it: Hitler came to power 'by the book', using Germany's democratic processes. This is what one historian says: 'Hitler's democratic triumph exposed the true nature of democracy. Democracy has few values of its own: it is as good, or as bad, as the principles of the people who operate it'. Two other remarks by people studying the way society works: 'Democracy can only work in an atmosphere of respect for, and promotion of, collective human rights.' 'The classic definition of democracy is not majority rule, but the protection of minorities.'