The document introduces aspect-oriented programming (AOP) as a programming methodology that aims to modularize code into distinct processes or concerns. It discusses how AOP can help address issues with traditional object-oriented programming (OOP), such as duplicate code from cross-cutting concerns that span multiple classes. The key idea of AOP is to define aspects separately from the core program and then weave them together using an aspect weaver. This allows cross-cutting concerns to be modularized independently from the core program logic.