Olap cube is online analytical processing concept used for extracting business intelligence. At it's core it's just a grouping of data by some dimensions and aggregation of values through facts. Facts can be sum, count, distinct and various others concepts. Cube can be made from various data sources: aggregates, snowflakes, SQL, LINQ, etc...

DSL example:

module Finance {
  aggregate Payment {
    Timestamp createdAt { versioning; }
    String    account;
    Money     total;
    calculated Int year from 'it => it.Year';
  }

  cube<Payment> Analysis {
    dimension account;
    dimension year;
    count     createdAt;
    sum       total;
  }
}