Why subreports are added only in detail band and crosstabs in summary? How actually the bands are processed in Jaspersoft?

I'm using subreports in Jaspersoft. Why we have to add subreports only in detail band why not in any other band?

Solution

I'm new to jasper reports so can anybody provide a tutorial name or give some detail explaination?

The iReport Ultimate Guide is very helpful guide.

why we have to add subreports only in detail band why not in any other band?

The subreport could not be placed to the band without overflow support.