There are libraries filled with answers to the first question. There is no quick, easy summation. It would necessarily be overly broad, and fallacious. The second question is answered with a literal translation of the Greek roots demos = the people, kratos = ruler. It is government by the people. However, pure democracy tends to turn into mob rule. Not only that, but the modern usage of the term conflates a pollitical system with an economic system, and people often say they want to spread democracy, when they really mean that they want to spread a free market economic system. In most current "democracies", the representative forms of government are actually far more similar to republics; however, they are distinguished from ancient republics by carefully wrought systems of checks and balances.