Object-Oriented Analysis and Design (OOAD) is a software engineering methodology that involves using object-oriented concepts to design and implement software systems.
OOAD involves a number of techniques and practices, including object-oriented programming, design patterns, UML diagrams, and use cases.
Design of a system consists of classes, interfaces, and collaboration.
UML provides class diagram, object diagram to support this.
Implementation defines the components assembled together to make a complete physical system.
UML component diagram is used to support the implementation perspective.
UML is a combination of several object-oriented notations: Object-Oriented Design, Object Modeling Technique, and Object-Oriented Software Engineering.
UML uses the strengths of these three approaches to present a more consistent methodology that's easier to use.