Users can place anything they want on the server. Whether it's a database, a teamspeak server, a rocketchat, a website, or something else. As a rule, companies that rent servers host a lot of applications there that help in their work. For example, companies that are engaged in calling customers place a database, a CRM system, an application for calling on the server and after that connect each user separately.
From personal experience, I can say that many companies use an external means to communicate with employees. For example, they can use Skype, Slack with an external server, and country email list so on. At the same time, it will be more prudent and safer to use a communication application that will be placed on your server. Thanks to this, you will be able to restrict the access of your employees so that they can use it only from the workspace, and you can also track correspondence and so on.
And so the list of what is usually posted is as follows
Website hosting
Mail server
Game server
IP Telephony Server
Virtual Workspace
Databases/data backup
Own VPN
Bots for messengers
This is not all that can be placed on VPS and VDS, but perhaps we will limit ourselves to this and go through each item, although we have already discussed a lot of this in other articles.