Harmonizers are attuned to people's feelings. They like to talk about people - not in the same way that Expressers do, but more quietly, drawing less attention to themselves. Their focus is the group's well-being, and their trademark is being a team player.
Harmonizers tend to avoid conflict. In social situations, they'll rarely say anything inflammatory or unconventional. Harmonizers prefer to fit in, not stand out. Because they like to please others, they often say "yes" to something though it would be better if they declined. As a result, Harmonizers can take on too much and feel overwhelmed.
In short, people naturally turn to Harmonizers for comfort in times of trouble. They keep people working happily together and are essential to a successful team.