Many organizations (including us) steps, slowly but surely, off of e-mail in favor of the chat app Slack. Microsoft was there before all of the competition participated in by Teams to launch. Now is that just as Slack is free to use.
Teams is just as Slack from chatkanalen around different topics, where colleagues can brainstorm and files can exchange. Until recently it was Teams only to use for those who have a paid Office 365 subscription ended, but now everyone can with the free version to get started.
This variant has some limitations compared to the paid Teams. Among others, there is no support for OneDrive integration, scheduling of meetings and the recording of it. Each user gets 2 GB of personal and 10 GB of shared storage, for an Office 365 subscription you get 1 TB space available.
Interesting compared to the free version of Slack is that Teams video-conference calls, where you are in Slack only 1 on 1 conversations. You can also play in Teams, invite guests who have no account, have to create, that is also not an option in Slack. Do you want all the features of Teams, then that will cost you a minimum of 4,20 euro per user per month.