From Oracle FAQ
Essbase is a database management system (DBMS) that provides a multidimensional database platform for builing OLAP applications. Essbase can provide sub-second responses to analytical queries.
To retrieve data from Essbase cubes, you need to use the Essbase Report Specification Language to generate report scripts.
Esbase was originally developed by Arbor Software, which merged with Hyperion Software in 1998. The name "Essbase" was derived from "Extended Spread Sheet dataBASE".
Until late 2005, Essbase was marketed by IBM as "DB2 OLAP Server".
Hyperion Solutions was purchased by Oracle Corporation in March 2007. Hyperion now operates as a subsidiary of Oracle Corporation.
Hyperion support moved to Metalink in May 2008.