This document is the first chapter of a textbook on robotic systems by Professor Ibrahim Hamarash. It introduces robots and discusses definitions of robots. It describes the diversity of robots in terms of size, design and capabilities. It discusses how robots are defined as machines that can sense their environment, perform computations to make decisions, and take physical actions. The chapter also categorizes robots by their application, including industrial, medical, military, and more. It further categorizes robots based on their locomotion and kinematics, such as stationary, wheeled, legged robots. The chapter concludes with an overview of robotic systems architecture and platforms.