Hi srik,
The idea of a tabular reference is that you can create a report with multiple queries (2, say), and instead of each query having it's own tabular model, you could reuse your work from one query in the other query.
For example, if you wanted the same data to be presented in both list and crosstab format within your report, you would need 2 queries. If you needed to define a really complex calculation within this process, rather than having to define it twice (once for each tabular model), you could define it just once in the tabular model of your first query, then your second query could reuse the contents of your first query via a tabular reference.
Best regards,
MF.