Office 365 provides the ability to have your tenant or users in your tenant be bumped up the line for new feature releases. Think of this as dropping a rock in water and watching the wave rings move outward. The closer you are to the center, you can get the new features first. Microsoft has this concept of Standard Release and First Release. In Standard Release, you get all the new features at a slower pace. In First Release, you get all the new features before Standard Release. If you opt in for First release, you can have your whole tenant (all users) get the newest updates or you can select users in your tenant. A good use case for the complete tenement being on First Release would be your lab environment. You want to see all the newest updates/features roll out here first, so that you can test how they function and the impacts on your user base. A good use case for select users being on First Release, would be a group of power users or pilot users in your production tenant. This gives the ability to see the new updates/features to a group of friendly users before they hit the rest of the production users.
For more information on Office 365 Release Preferences, see the KB below.
Office 365 Release Preferences
In this example, I will show how to enable first release for select users in a tenant. First release for everyone, is pretty much self-explanatory.
Login to the Office Admin Center
On the left navigation menu, click Settings
Click Organizational Profile
Click Edit on Release Preferences
In the flyout, select First release for selected users
Click Yes when asked ‘Are you sure you want to change to first release for select people?’
Click Add People
Select the users
A list of users under First Release will now be displayed
You can add/remove users by coming back into this menu and clicking +Add Users or –Remove Users