Well Retweet feature lets you to get a simple button that will simplify and ease the process of sharing interesting tweets with your followers.
This is what Twitter stated in its blog:
We’ve just activated a feature called Retweet on a very small percentage of accounts in order to see how it works in the wild.
Initially this feature was rolled out for the limited users, and now it is available for most of the users almost all of them. Even I can use the Retweet feature again.
I am so happy to see this Retweet feature back. Even most of you will be.