Tartuffe represents religious hypocrisy. He cons Orgon by pretending to be a religiously devoted and pious person who denies himself and spends his time involved in charitable works to help the poor. He persuades Orgon to sign his house over to him and to leave his inheritance to him.
Tartuffe has not a religious bone in his body and even tries to seduce Orgon's wife. He is all good words and no good deeds.
Tartuffe exposes the vice or evil of cheating and lying to get hold of another person's possessions, but he also exposes Orgon's vice of being too trusting. As the genuinely good Cleante says
The truly pious people . . . are not the ones who make the biggest show.
Orgon's vice is being too willing to believe words rather than looking at what a person does. He longs to find an individual of true Christian goodness in an evil world, and so he falls for a person who tells him what he wants to hear. At the same time, he misses the family members and people around him who are truly good, even if they don't entirely express themselves in the religious language Orgon wants to hear.