General comments about the diagram

1. The solid colored heart. The heart is central to all instruction. In designing a lesson, the objectives, selection of content, skills, and evaluation must be determined first. The heart has three parts and each part is represented by the one crucial element of lesson planning.
2. The striped circle. After the first step of lesson planning is completed, the lesson is furthered developed and made ready for implementation.
3. The shaded square. It indicates that lesson is taught. When the lesson is taught, all the previous components come into play: The circle and heart are placed off centre of the square representing that although they are important to planning they are not centre to the interaction of teaching.

Notice in the diagram the heart is larger than the circle. This indicates that these three elements (objectives, content and teaching strategies, and evaluation of the learning) of the heart will and can change as the lesson is taught.
Remember a lesson plan is a plan. Plans change when they are implemented.