Section 90.3 addresses the arrangement of the Code, or the way that it is laid out. The NEC consists of the introduction, which is Article 90, followed by nine chapters.
Chapters 1 through 4 provide very general requirements, covering all kinds of installations.
Chapter 1 includes definitions in Article 100 and Article 110 covers working space and general information.
Chapter 2 includes things like the specific details of branch circuits, feeders and services, as well the general requirements for grounding.
Chapter 3 includes the requirements for selecting conductors and wiring methods. While Chapter 2 provides the requirements for protecting those conductors from overcurrent. Chapter 3 includes other requirements for wiring methods, such as the different kinds of cables and raceways that can be used in making an installation.
Chapter 4 covers common types of equipment – switches, receptacles and panelboards – along with motors, air-conditioning equipment and transformers.