ITIL and COBIT both are framework for IT. What are the overlapping or common areas of these two frameworks?

Actually hCOBIT and ITIL don't really overlap in the way most people would consider overlapping.  They are more complementary.  Cobit is a framework of controls (regulations, checks/balances) that auditors use to identify and measure IT gaps against their controls.  These controls are a mix of technical level, and process/procedural.  Cobit also goes across IT silos (Software, Infrastructure, Security).  ITIL is a framework focused on creating and managing technology Services.  Mostly focused on Infrastructure or end user consumed IT services.  I know these are very simplistic examples and not complete but I needed to get that out of the way before I talk about the over lap.

Cobit will have a number of control points that must be met, and often these are fulfilled by different lower level, or more appropriate frame works.  Some of the Cobit controls require the implementation of checks/balances and the common framework to fulfill some of these is ITIL.  In some other cobit controls SDLC or some other framework is applied.

So, there is not a traditional "overlap" but more of complimentary and supplemental relationship between COBIT and ITIL.

Here is a image of the touchpoints, between cobit and ITIL.  But this is not all of the COBIT controls, there are many more.

http://intreis.com/wp-content/uploads/2014/06/Cobit-ITIL-Mapping1-1024x886.jpg