Please can anyone help me understanding the GT & where to use each and every symbol and the purpose?

There is no one place to learn it all. The basic principles of GD & T are to establish controlled limits to parts the go beyond basic linear dimensioning. ASTM Y14.5 is a commonly referenced standard. Wikipedia has a good brief description on the symbols and there usage.
If you really want to learn the ins an outs most colleges have a GD&T class.

In my experience, GD&T should be avoided like the plague, as it generally causes confusion and excess cost. That said the best reference I have found is the Astm standard mentioned above.
When you are going to use GD&T, be sure you understand what your need is and how to explain the need to others, so that you end up with the desired result.

see attached flash file..
actually gd&t are the engineering symboles that nessecery to manufacture a designed part. part are not be manufactured as per exact dimensions,, some dimensions error are come. so gd&t is allow the limit of acceptabe dimensions as per function & all other like assmemble...so gd&t is a broad area that can not be complete here. and also it useful to design zig & fixture to guide & locate for machining,,

GDT when properly applied should make your part cheaper. That's if and only if everyone understands it. More and more companies are moving to its application. It is growing in popularity so i would suggest learning it like a second language, the sooner the better.

any books or references to learn

ASME Y14.5 is the standard (which cover almost all the intricate details about GD&T) But to start with you could start looking into TATA mcgraw hill publication books in GD&T. If you want to learn online "ETI" could be one good place to look.

Here. Read Chapter 5 and possibly beyond that. This is an older version than the current standard in ASME Y14.5 2009