A service that automates lift-and-shift (Rehost) migration of physical, virtual, or other-cloud servers to EC2, continuously replicating the source servers and allowing test cutovers and final cutovers with minimal downtime.
In SAP-C02 it's the recommended tool for the "R" of Rehost among the 7 Rs. It replaced AWS SMS (Server Migration Service, deprecated). Question: migrate hundreds of on-premises servers to EC2 without redesigning the application → MGN.
AWS Application Migration Service (MGN) is a concept that can show up on the exam. Check the full guide to see it in context.