Straight from the Message Center!!

Microsoft To-Do is an updated Office 365 feature.
We’ll begin rolling this change out in mid-March and it will finish by the end of the month. This enhancement is related to Microsoft 365 Roadmap ID 34338.

How does this impact me?
The To-Do web app license will soon licensed as part of Exchange Online. There are no changes to the To-Do licenses for the downloadable To-Do apps for Windows, iOS, and Android, as well as the Microsoft 365 app launcher tile.
What should I do to prepare for this change?
You don’t need to do anything, but may consider updating your user training, and notifying your helpdesk.