This document provides an overview of OpenStack, an open source cloud operating system. It discusses that OpenStack is used for public, private, and hybrid clouds, and functions as an IaaS framework. It then summarizes the core components of OpenStack including Nova (cloud controller), Neutron (software-defined networking), Cinder (block storage), and Swift (object storage). The document also briefly mentions other shared services like Keystone (identity), Glance (images), and Heat (orchestration).