We don't have a democracy. It's a republic. Basically a fake democracy.
Republic tells you who is sovereign: the people--as opposed to a monarchy.
Democracy tells you how decisions are made: by voting--as opposed to a dictatorship.
You can have a democracy that is not a republic: Great Britain.
And you can have a republic that is not a democracy: North Korea.
The U.S. is a democratic republic.
if by "the US" you mean "the collection of various states that make up the members of the federal government of the united states of america", than there isn't one single concept that can be applied universally.
different states have different types of governments - some are even commonwealths, not states!