Hey there!
The government of Athens was very shaky until it was firmly put into place.
After being ruled by Monarchs, Oligarchs, and Tyrants, Cleisthenes, father of democracy, created the foundation for our modern government.
All citizens had the right to vote and participate in the assembly, and it was considered their civic duty to do so.
However, a citizen wasn't just anybody.
A citizen was a free male person over the age of 18 years old and was born in the city-state of Athens.
That really narrowed it down.
Therefore, it was ruled by the people, but not just any people.
If you want to know about how the ruling was in other forms of government, the monarchy was where the monarch inherited power and the monarch's word was law, oligarchy was when rich aristocrats ruled in favor of the wealthy and the rich got richer while the poor got poorer, and tyranny was when a leader rose to power from military support. In that time period, tyrants were usually respected and often had goals and ideas that were in the best interest of the people.
Hope this helped!