What is lightning migration in Salesforce?

Salesforce Lightning Migration from Salesforce Classic does not require to import the data, regenerate custom fields, or set up the security model. However, there are few aspects to the Lightning Experience that need a check during the migration of the data, such as:
Custom Code: The custom code created might not perform well in the Lightning version and might need to be addressed.
Business Processes: Going through the business processes again is advised to synchronize the requirements and experience how Lightning can overcome obstacles differently.
User Interface: The new Lightning Experience consists of 3-column layouts, up to 25 tabs, Paths, Components, etc.
3rd Party AppExchange Apps: With the Lightning-Ready 3rd party AppExchange apps, inventory management becomes much more feasible and attainable.
User Training: Current users need to be trained again to ensure that the adoption of new Lightning features is productive.