An overview on the differences between a migration and a transition, and when you would use either method.
A migration is the transfer of data between services. In this situation, a new service is provisioned and all the information copied from the previous service to the new service.
This requires creation of a new service including configuration, licenses, domain verification, adding of users, distribution lists, contacts, delegated rights, etc.
Then all data (eg emails) need to be copied across to the new service, and then the customer devices reconfigured to access the new service.
You would use a migration if you were changing from one service to a different service. For example, GSuite to Microsoft 365, MPexchange to Microsoft 365.
A transition is the transfer of billing or support services from one vendor to another.
The service's data is not altered, all emails and stored files remain in the same place and intact, no data movement is required.
You would use a transition if you are changing to another provider for the same service. For example, changing your Microsoft 365 license provider from Microsoft direct to Manage Protect.