I'm going to apply for graduate studies and one of the SOP outline points says
Have strong opening and closing paragraph
What could be considered a strong paragraph? In my case, the opening paragraph is a mild introduction, not describing things in specific terms, but giving some base points. The closing paragraph sums up the middle-ware (mostly education, work experience and other interests), states my academic goals and future perspective.
Do I understand them, the paragraphs, properly?
Strong is subjective and likely to mean one of two things, either thought provoking or emotionally moving (and possibly both). In general a closing paragraph should not only summarize what has been said before, but synthesize a new statement (or direction of inquiry) from the supporting statements. In academic papers, one leans more towards logic and less towards emotion, however in a proposal like this, you want to get your reader excited about your idea.
You want to stand out for the work you plan to do. Use language that is not 'soft', be confident and point towards facts. Show how your ideas will lead to increased knowledge or productivity and do not make it about you.
Use your conclusion to state how your idea builds on what you have done, what others of done and what positive advances it might lead to if the work is done. Then you might state how this has inspired you to pursue this field.