In simple terms, the Achievement Program (AP) is a travel guide, to help you on your journey through the world of model railroading. The AP also provides incentive to learn and master the many crafts and skills necessary in the hobby of model railroading. With the completion of each category, you will be issued a certificate acknowledging your achievement.
The AP requirements are a set of standards, but they can also serve as a set of guideposts for those who are new, near-new, and not-so-new to the hobby. Not because they lead to some sort of official pat-on-the-back, but because they are a source of ideas for projects that can help us learn to become better modelers.

nmra.org