Ashwin,

In a nutshell, object orientated design is an approach for certain technical solutions and relies on a concept of "objects" to which the design is "orientated". An object is real world thing or an event between 2 real world things, AND the methods for maintaining that object.

Example: Customer and Product are real world things. "Sale" is an event between these two real world things. The object Customer would be all the information in scope for Customer and all the methods of creating, reading, updating and deleting Customer objects.

There is a hellavalot more to this subject area: libraries of books, petrabytes of web stuff, more courses and training material than you can shake a stick at, so I can't really go in to too much detail! Google it and you will be rewarded with several lifetime's worth of material!

Guy