A list of objectives can help you to gauge whether or not your students have achieved everything they should have once the lesson is over. Depending on the subject matter, objectives might be practical, for example, what can the student do at lesson completion. The objectives could also be knowledge based, for example, what does the student know after the lesson is complete.
Are you planning on teaching a class? If so, lesson plans provide you with a variety of different advantages. Any experienced teachers will tell you that having a plan does wonders for smoothing out the most chaotic of classes. Others, however, will tell you that sticking too closely to the plan will make things needlessly complicated and that flexibility is the key to running a sound classroom. In truth, both sides have merit; the best way to run a classroom, particularly one filled with younger, excitable students, is to maintain a perfect balance of order and creativity.