Civic virtue means how good we are at being a part of our community and doing things that are good for everyone in the community. It means that we care about other people and do things that are helpful for all of us to live together nicely.
It is like being a good friend to everyone in your class. If you share your toys, help your classmates, and play nicely with everyone, that's being a good friend, right? Similarly, if you try to help clean up the park or volunteer to help old people in your community, that's showing civic virtue.
It's also like being a good citizen. When we vote, participate in town meetings, or obey the laws, we are doing our best to help our whole community, not just ourselves.
In short, civic virtue means being a good person who cares about others and takes responsibility for making the community a better place for everybody.