In the early days of Athens it was ruled by Kings, but in 510BC Cleisthenes drove out the last of them, and created the world's first democratic government.

"Demo" means common people, and "Kratos" means power.

This was not the modern sense of democracy. Not everybody was allowed to vote. Only the freeborn Athenian males.
Women were not regarded as citizens, so therefore had no vote at all. Neither did foreigners or slaves or descendants of slaves.
The city was divided into ten blocks called tribes. Each tribe elected 50 men over the age of 30 to a council which carried out the function of government.