Microsoft's Work Folders, which is for organizational accounts, allows you to sync work files across devices and access them while offline. For important internal documents, having employees using their own computers and phones to access them is a bit of a security nightmare. Work Folders is a compromise, adding some more protection—and convenience—to allow people to work with potentially sensitive information that is stored on an organization's server.
While this feature is well-integrated into Windows (as you might have expected), this is its debut on Android. If you do not have an account with access via your employer, it won't do you any good; this is a subscribers-only feature set.
Security features include at-rest encryption, meaning if someone grabbed your phone and scanned its contents, the files would not be usable without a passkey. The app itself can be locked with an app password. It also integrates with other device policies, like those that may require you to use a lock-screen pin code. And since the organization still has control, access to files can be revoked remotely while a variety of other per-user permissions are available for administrators.
This appears to be a soft launch, since Microsoft's documentation doesn't mention it just yet. If your employer has enabled this feature, check it out.