Can somebody define "virtue" for me?
You could say that a virtue is something that makes acting morally easier. Of course since actions reinforce like habits, good acts generally contribute to virtues. But the virtue itself is more like a character trait. For example, an honest person is more naturally inclined not to lie, so this trait of honesty is a virtue.
Aquinas defines it as follows:
"Virtue is a good quality of the mind, by which we live righteously, of which no one can make bad use, which God works in us, without us."
The last clause is probably the most troublesome at a general glance, but it is a Christian view. It is essentially saying that no one does good except through God. A person is involved in a turn towards virtue insofar as they direct their will to that end, but without God's intervention no acquisition of virture would be possible.
Is there an absolute virtue?
Well, you can speak of virtue in general and certainly virtues do work in such a way that doing good specifically helps one to do good generally. But usually we talk about specific virtues. Of those you could say that Faith, Hope, Charity (Love), Prudence (Wisdom), Justice, Fortitude (Courage), and Temperence (Moderation). Of those Faith, Hope and Love are more important and the greatest of those would be Love.
Is there a sense of right and wrong that can be agreed upon?
Right and wrong that exist? Certainly. That we'll agree upon? Probably not.
