This document provides an overview of Intelligent Tutoring Systems (ITS). ITS are computerized learning environments that incorporate models from cognitive science to closely mimic individualized human tutoring. The document discusses that ITS track students' knowledge and skills in detail through student modeling. It also describes the typical architecture of an ITS which includes domain models to represent expert knowledge, student models to track individual learners, tutoring models to determine instructional interactions, and interfaces to interact with students. Examples of ITS like Cognitive Tutors and Andes physics tutor are also briefly mentioned.