Unhappiness is subtracted from the Happiness that your Civ produces. This Guide's focus will be to first help you understand where Happiness/Unhappiness come from, then teach you all the different methods of acquiring Happiness and managing Unhappiness in order to avoid penalties and keep your Cities growing.
Sink too far and Rebels may pop up in your lands, or, far worse, you could lose Cities to another Civilization once Ideologies are chosen. Having a negative Happiness score results in Unhappiness and greatly slowed City Growth, Production, and Combat Penalties for your Military. Happiness is an essential resource in Civ 5 which allows Cities to grow and Empires to enter Golden Ages. Civ 5 Happiness Guide Golden Ages & Managing Unhappiness in Your Empire Civ 5's Happiness allows Cities to grow and Empires to have Golden Ages