It is a mature, open source object-relational mapper for the .NET framework. It's actively developed, fully featured and used in thousands of successful projects.
It is a lightweight, extensible, open source and cross-platform version of the popular Entity Framework data access technology. It can serve as an object-relational mapper (O/RM), enabling .NET developers to work with a database using .NET objects, and eliminating the need for most of the data-access code they usually need to write.
Hibernate is a suite of open source projects around domain models. The flagship project is Hibernate ORM, the Object Relational Mapper.
Sequelize is a promise-based ORM for Node.js and io.js. It supports the dialects PostgreSQL, MySQL,
MariaDB, SQLite and MSSQL and features solid transaction support, relations, read replication and
Doctrine 2 sits on top of a powerful database abstraction layer (DBAL). One of its key features is the option to write database queries in a proprietary object oriented SQL dialect called Doctrine Query Language (DQL), inspired by Hibernates HQL.