The Doctrine Common annotations library was born from a need in the Doctrine2 ORM to allow the mapping information to be specified as metadata embedded in the class files, on properties and methods. The library is independent and can be used in your own libraries to implement doc block annotations.
The Doctrine Migrations offer additional functionality on top of the database abstraction layer (DBAL) for versioning your database schema and easily deploying changes to it. It is a very easy to use and powerful tool. To use the Migrations as supplement you have to get the sources from the GitHub repository, either by downloading them, checking them out as SVN ...