Oracle Corporation is an American multinational computer technology corporation, headquartered in Redwood Shores, California.
PostgreSQL, often simply Postgres, is an object-relational database management system with an emphasis on extensibility and standards compliance.
MySQL is an open-source relational database management system. Its name is a combination of "My", the name of co-founder Michael Widenius's daughter, and "SQL", the abbreviation for Structured Query Language.
SQL is a domain-specific language used in programming and designed for managing data held in a relational database management system, or for stream processing in a relational data stream management system.
SQLite is a relational database management system contained in a C programming library. In contrast to many other database management systems, SQLite is not a client–server database engine. Rather, it is embedded into the end program.