Migration in Rails is a tool that utilizes Ruby code to modify an application's database schema, offering database independence and facilitating platform transitions. Defined using a domain-specific language, these migrations are stored in files within the db/migrate directory, named with a UTC timestamp and a descriptive title, and their class names must match the file name's latter part. Migrations allow for creating tables, adding indexes, and modifying columns, with changes encapsulated in methods like 'change' for database manipulation. Errors during migration, such as duplicate column errors, can be managed by Rails's transactional execution, which rolls back upon failure to maintain database consistency. To minimize migration errors, best practices include rolling back migrations to resolve issues, cleaning up old migrations, ensuring reversibility, and using temporary rake tasks for complex data changes. Additionally, tools like Rollbar can automate error monitoring and management, enhancing deployment confidence by tracking and analyzing errors in real-time.