CloudWatch dashboards are personalizable home pages in CloudWatch console that allows us to monitor all the resources that are spread across various regions in a single view. CloudWatch dashboards are used to create metrics, alarms in a single view. Also, for displaying graphs and widgets from different AWS accounts and different regions.
I suggest enrolling in this AWS Migration Certification course by Intellipaat if you want to learn AWS data migration.
Also, watch this video on Amazon CloudWatch: