Object-Oriented Analysis (OOA) is a technique developed by Coad and Yourdon to model system functionality using objects. There are five major activities in OOA: (1) finding classes and objects, (2) identifying structures like generalization/specialization and whole-part, (3) identifying subjects, (4) defining attributes, and (5) defining services. OOA provides a consistent way to represent a problem domain using objects and can help tackle complex problems, improve communication between analysts and domain experts, and increase consistency while building resilient specifications that can be reused.