Let us start by looking at what cubes are NOT…

Cubes are not relational databases.

Microsoft Dynamics NAV, AX, GP, and SQL are all examples of relational databases.  Relational databases include tables and fields which are joined together by keys.  Relational databases are great – we couldn’t run our businesses without them.  They are optimized to get information into a system in a cohesive manner.  But frankly, they are not optimized for getting the information out of the system.

- Continue reading at: OLAP Cubes 101 (PDF)