Democracy enables people to elect public officials. That's all. That's in contrast to countries that are ruled by people that are not democratically elected, such as kingdoms or militarily controlled regimes.
But the right to elect one's government officials doesn't guarantee a free society. Freedom is determined by the powers wielded by the government. If government's powers are limited to their legitimate function, then people in that society will be free. And that's true whether government officials are democratically elected or not.
In other words, theoretically an unelected regime could result in a freer country than a democratically elected one. An unelected regime, for example, could implement a free-market economic system while a democratic one could implement a welfare-state, managed-economy system. Or an unelected regime could establish a system with a small military and no CIA or NSA while an elected regime could establish a national-security state.
The only real benefit of a democratic system is that people can peacefully change public officials, especially when there is a change in overall philosophies within society. With unelected regimes, the only way to change officials is through revolution, which can be costly in terms of life, property, and money.