En su propia web lo definen como:
Gitter is a chat and networking platform that helps to manage, grow and connect communities through messaging, content and discovery.
Entre sus características está:
Free without limits
Enjoy free public and private communities with unlimited people, message history and integrations.
Simple to create
Simply create your community and start talking – no need to set up any invitation services.
Markdown and KaTeX
Format your messages just like with your other favorite developer tools.
Out in the open
Complete history archives(indexed by search engines) and sharable permalinks or use Sidecar to embed Gitter directly in your own site.