With Slack, team members can send and receive all kinds of relevant information and mention specific people to prevent them from missing a message. On the other hand, you can synchronize the app with Dropbox, Tello or Google Drive services, making it easier to send and access files stored in the cloud that you need to share with your colleagues without having to browse between apps.
One of its most interesting features is the possibility of creating different conversation channels with different team members. Thus, each of the departments can have their own channel, in which to discuss only content relevant to that particular department. Plus, you can root messages within the same conversation to create sub-conversations in which only the users who are concerned participate.
Slack also offers a JIRA technical service and other tools such as statistics or videoconferencing through third party apps. Also, since it doesn't have a user limit, all employees can keep up to date at all times, regardless of the size of the company.