Meeting Migration Service (MMS) is a service that runs in the background and automatically updates Skype for Business and Microsoft Teams meetings for users. MMS is designed to eliminate the need for users to run the Meeting Migration Tool to update their Skype for Business and Microsoft Teams meetings.
— Read on docs.microsoft.com/en-us/skypeforbusiness/audio-conferencing-in-office-365/setting-up-the-meeting-migration-service-mms