Dynamics 365 version 9.0 has two user interfaces now
1 – Web Interface
2 – Unified Interface
Which means, that users have the choice to select, either the classic view (Web interface) or the modern experience (Unified Interface). The Dynamics 365 administrator can also manage this for the users.
Web interface is quite confusing and complex for users, however Unified Interface is simple, intuitive and focused. Unified Interface works like an app and the experience is same on the laptop, tablet and mobile phone.
The experience is unified, means if you are changing a record in Dynamics 365 “Sales – Web Interface”, it will reflect in an enhanced user experience in the “Sales – Unified Interface App”. However, there are certain limitations, that Microsoft is working on.
For example, if you edit the system dashboard “Sales Activity Social Dashboard” in the web interface, the changes will not be completely reflected in the unified interface app.
For more release and limitations, please refer this article: