This document provides an overview of Project Ara, which aims to redefine smartphone hardware and Android architecture through a modular design. It discusses the origins and goals of creating an open, modular smartphone platform from initiatives at DARPA and Motorola/Google. The key aspects covered include the module ecosystem where third parties can create customizable modules, technologies enabling the modular design like capacitive connectors, and the software architecture changes needed to support hot-swappable modules running on Android. Challenges across hardware, software, manufacturing, and compliance are also discussed.