Save as Draft functionality I have created a content type, and while adding content under this content type I wanted to provide author, the facility to save this content as draft which he later can edit and publish, ideally, a button with "Save Draft" besides "Publish" button. Is there any drupal module that provides such functionality. I have gone through "Save Draft" module, but I don't understands it exact functionality, it is just providing a button with label, what exactly is is doing is not clear to me. Please help me if I am missing something.

Thanks for your time.
What would the main use of this? If a content is kept as unpublished it is similar to saving the draft. It will not be visible to anyone else except the author and admin and any one else you have given permission to view the same. So this in itself is a good option. The save as draft module does the same thing it creates a button to uncheck or check the publish unpublish checkbox. 

If you are looking for a workflow kind of feature then workflow module would be a better option. where you can define different workflow status and give different users permission to access the node in each workflow state.