For cloud SaaS apps, SSO is trivial – simply configure the corresponding Enteprise App in AAD – and configure SSO in there.

What if you have Infor Web Apps hosted On Premises – and want to implement SSO ?

Infor STS (MINGLE 12, built into Infor OS) is an alternative to adfs, for customers looking to replace ADFS.

STS, in this case is serving as a Service Provider. The IdP  can be anything – including AAD (also okta, ping, adfs, netiq, oracle access manager…).
What is the End User Experience?
The user experience for AAD will display the familiar Microsoft login screen for SSO (if not already logged in)

Infor sts as an identity provider?

Yes – Infor STS can also act as an IdP and connect to LDAP