Does anyone knows what is meant by Activation record of a 'procedure'?
It comes under the principles of Compiler design. I guess very few people know the fundamentals of compiler design.
I took a course on compilers before, and even helped write a compiler for a subset language of java.
AR is pretty much equivalent to stack frames. In your case, an AR of a procedure is pretty much a "new environment" for local var declarations and such. It scopes the local variables in the new procedure from being seen outside, yet the new environment will contain records (if there are any) of the previous environment (i.e. outside the call of the procedure).
In a nut shell, think of stacks. And the thing you're pushing are pretty much scopes of your methods. When your method finishes, the stack will pop, and you'll be in the previous method prior to calling the method that just popped off.
Whenever you call a procedure there are certain informations the program associates with that procedure call. The return address is a good example of some information the program maintains for a specific procedure call. Activation record is the term we'll use to describe the information the program associates with a specific call to a procedure.