Civics are government policies you can use to better rule your people. Each civic provides you with certain advantages and disadvantages. You decide what's the best civic for your current situation.
There are four civic groups (Government, Labour, Economy, Magic), each including several civics. Only one civic can be active in each group so you'll have four active civics at any time.
In order to become available, civics must be researched first. Their effects will be active as long as the civic is active.
You can switch civics in the Governing Adviser. Changing civics will lead to anarchy for a brief period of time.