Features

Slack offers channels organized by topic, as well as private groups and direct messaging. All content inside Slack is searchable, including files, conversations, and people. Slack integrates with a large number of third-party services and supports community-built integrations. Major integrations include services such as Google Drive, Trello, Dropbox, Box, Heroku, IBM Bluemix, Crashlytics, GitHub, Runscope and Zendesk.  Users can add emoji buttons to their messages, which other users can then click on to express their reactions to messages.

Teams

Slack teams allow communities, groups, or teams to join through a specific URL or invitation sent by a team admin or owner. Although Slack was meant for organizational communication, it has been slowly turning into a community platform, a function for which users had previously used message boards or social media such as Facebook or LinkedIn groups. Many of these communities are categorized by topics which a group of people may be interested in discussing.

Messaging

Public channels allow team members to communicate without the use of email or group SMS (texting). They are open to everyone in the chat provided they have first been invited to join the client. Private channels allow for private conversation between smaller sects of the overall group. These can be used to break up large teams into their own respective projects. Direct messages allow users to send private messages to a specific user rather than a group of people. Direct messages can include up to nine people (the originator plus eight people). Once started this direct message group can be converted to a private channel.