# Zulip User Documentation Zulip is a group chat app. Its most distinctive characteristic is that conversation within an organization is divided into “**streams**” and further subdivided into “**topics**”, so that much finer-grained conversations are possible than with IRC or other chat tools. Most people use Zulip on the Web. There are also mobile apps for Android/iOS, and desktop apps for Mac/Linux/Windows, which can be downloaded [here](https://zulipchat.com/apps/). One Zulip account, associated with a particular company, project, or team, is known as an **organization**. {!sidebar_index.md!}