What is the difference between effective and efficient teaching?

Allow me: Efficient teaching might be construed as going in with a lesson plan, addressing every point on the plan, and coming out on schedule. Effective teaching might be going in with a lesson plan, addressing every point on the plan, observing every student's apparent understanding and trying presentations until all the light bulbs turn on. You might come out behind schedule. But you've been effective and efficient both with the emphasis on "effective".