Essbase is a multi-dimensional database that has been around for some time. It is the basis for Oracle Planning and a lot of the Oracle EPM cloud tools (PBCS, EPBCS, FCCS and so on). It's also used to store the balances in Oracle Fusion Cloud GL.
Essbase stores and aggregates data according to the hierarchies defined in each dimension. Users can then use reporting tool or a simple Excel plugin to navigate the data, slicing and dicing down to narrow their query on the exact data set they are interested in.