Can anyone please let know difference between LPAR/DLPAR/WPAR.
and its purpose ???

A DLPAR (Dynamic Logical Partition) is a LPAR that you can reconfigure dynamically without shutting down the OS running there.
What I read about WPAR (didn't work with those) says they are for OS level virtualisation giving you the opportunity to isolate your applications under AIX.

You can also check Wikipedia or IBM's documentation and Wiki about Power Systems and AIX. Easy to find, really.

would be better to think of DLPAR as an operation to dynamically alter a virtual machine aka LPAR.

WPAR can be seen as the AIX implementation of the jail concept. Solaris has a similar construct known as containers. WPAR differentiate from others in that there are two types - system and application WPAR's.
An application WPAR isolates the application encapsulating the application in a protected environment that can be moved between AIX systems running at the same level.
A system WPAR appears as if it is a regular system. if you know where to look you can see the difference. System WPAR are also mobile capable.

Hope this helps.