so what is exactly the function called if not a class constructor?
It is a method. The developer should have put a comment in the file describing what the method is for.
What is also a return value sir?
It is a value that a function returns. The recognize() method returns some value when it gets done. The documentation tells you what the value is/means.
Where can i get that value based on my project?
WalMart. I really don't understand the question. If you want to say "Left field" to make a LED turn on, you need to define an entry in a a group. The group number is the first entry in the buf array that is populated by the method.
The rest of the values depend on code that you have not posted. Post ALL of your code AND a link to the library.