@girish it's the Community Edition you'd need in order to provide their collaboration features: document management, CRM, Projects, Mail aggregator, Calendar and Wiki. They also have an optional Mail Server.
I've just installed Community Edition on DigitalOcean; it's a great alternative to Nextcloud (their collaboration apps like CRM and Projects look really great) but the big downside for me is that there's no desktop/mobile device file sync. Everything stays in the cloud, you can only edit word, presentation and spreadsheet documents and only by using their desktop app or mobile apps, and you have to be online. You can connect a bunch of file sync services like Dropbox, Google Drive, etc via authorisation keys, which is nice, but I'm looking for an alternative to Dropbox, not more dependency.
You can also connect Yandex Disk or Nextcloud accounts with a user and password but it seems a shame to have to run Nextcloud just for file sync. I tested this and working with files in Onlyoffice via this webdav link to a Nextcloud server is slow, the invisible system files created by macOS Finder are visible, and I keep getting an error when I trying uploading a file created on my desktop by my CAD software, with a note to say that "all documents uploaded will be converted to Office Open XML format for faster editing". Completely daft.
This inability to sync files between computers and devices and use third-party apps to edit them is a showstopper for us. Which is a real shame because their collaboration modules look fantastic.
Document Server + Community Server + Mail Server (optional) = Community Edition (but with the limitation of 20 simultaneous connections to doc editors)
Document Server + Community Server + Mail Server (optional) = Enterprise Edition (limitations depend on the tariff plan)