During the job search process, it can start to feel like it's all about you. Your skills, your experience, your education, your dreams. Certainly it's important to communicate what you have to offer a company or organization, as you are the only one advocating for yourself. But once you get into a new job, no one's going to care anymore what experience or skills you brought with you, except to the extent that it helps you do your job well.
So it's important that throughout the application process — from the cover letter to the interview — you keep in mind both what you want to communicate about yourself and whatever it is that will become your focus once you get the job.
What that focus is will depend on the company or organization. At one place, the goal may be all about the bottom line — how you can maximize profit and keep shareholders happy. At another, the focus may be on the products the company produces and the positive impact they have on the world. For a non-profit, the most important thing is improving the lives of their clients, while a school is focused on helping their students succeed.
Of course, at many places there is a gap between the company's mission statement and what employees actually care about on a day-to-day basis. For the purpose of your application, though, you need to be able to speak the language of the mission statement. By talking not only about what you can do but also why that's important (e.g., it saves money, it improves services, it enriches the lives of others), you demonstrate that you are prepared to work alongside a hiring manager to accomplish the things they strive to do every day.