This document is a detailed study of Twitter conducted by Fabernovel and L'Atelier in December 2009, exploring its rapid growth, user demographics, functionalities, and potential business models. It describes Twitter as a unique public micro-blogging platform, distinct from traditional social networks, where users interact through short messages known as tweets. The study also discusses Twitter's usage in various sectors, including individual users, bloggers, companies, and public institutions, while analyzing competition with platforms like Facebook and Google.