Democracy - What is it?

"Democracy is the worst form of state, except for all those others that have been tried from time to time." (Winston Churchill)
Winston Churchill says it with British humor: democracy is valuable. And we know that democracy is not a matter of course. A large part of humanity still lives today in conditions that we understand are not democratic.
But what does "democracy" mean? What makes her? What forms of democracy are there? What can we do to protect our democracy?
We want to talk to each other on the occasion of the "month of democracy."