Reti opening(Nf3)is a strong defensive line for white.It is usually converted in other lines.
A closer look: Reti opening

It's not a defensive line, it's a good attacking tool. You stop 1...e5 and fight for control of the center, fianchettoing one or two Bishops in the process. The one problem is that it can often transpose into other openings like the English or QGD.
The Reti itself is 1.Nf3 d5 2.c4. It can be more of a move-order gimmick rather than a separate opening if it goes into something else.

I'm not going to teach you the Reti in a forum topic. You can easily buy a book and study it as presented by a GM. There are several good books on the subject.

It appears you do have access to the Internet, so you could purchase a book on amazon.com, for example.

Just by putting in RETI to the keyword search, this stuff came up. That'll keep you busy for a while.

It is too complex to cover in a single forum topic, especially as white often has a wide variety of choices to choose from, including multiple transpositions into independent lines more often occuring from other first moves.
In general 1.Nf3 serves the purposes of:
(a) Developing
(b) Taking control of ..e5.
Following the majority of blacks moves such as 1..c5 1..d5 1..Nf6 etc is it logical to play 2.c4.
As we have e5 under control, we should next look to control d5 via the use of c4, Nc3, g3 and bg2. That is the purpose of the classical setup.
Moves such as 1..d6 and 1..Nc6 which contest e5 can be logically answered by 2.d4.
You see that we play accoring to controling the centre. However, from here the plans vary drastically between the different setups black may choose. I suggest you find some online resources that cover the most common black setups, and, if you have a question, make a more specific forum topic. The current one is too broad.
I want to play Reti opening but I don't have any knowledge of it. I want to understand its stratagies,plans,ideas,further replies,variations and other helpful things in this line.