What is the difference between a trustee and an instructed delegate?

In Congress, there are two different ways elected legislators can act. One way is to act as a trustee. This means that the legislators vote and act according to their own personal beliefs and what they feel is best for society. This way is very personal, assuming that the voters trust the elected legislator to make the right decisions. The other way is to be an instructed delegate. Unlike the trustee, an instructed delegate is an agent of the voters, voting according to what they want even if they don't wholeheartedly agree to what the people want.