An OLAP Engine is used for enabling fast ad hoc queries by end users. A user can interactively explore data by drilling, slicing or pivoting.
?    Drilling refers to the process of exploring details of the data.
?    Slicing refers to the process of placing data in rows and columns.
?    Pivoting refers to switching categories of data between rows and columns.
?    In OLAP, we will be using what are called as Dimensional Databases.