Civil has several meanings. The simplest is cultured and polite, as in someone who is civilized. Civil can also describe things related to a community of people and their government, or a civilization.
If you work for the post office, you're a civil servant. The Civil Rights movement focused on the notion that all American citizens were entitled to the same basic personal rights and freedoms. Civil wars are named in reference to the fact that conflict occurs between citizens of the same country, and civil law is similarly limited to non-criminal issues that community members have with each other. The Latin root, civilis, means both "relating to a citizen" and "courteous."