In conference review process, what do "author response" and "author notification" mean? I just visited a conference website where organizers, for the submitted paper review process, listed a date for paper submission, a date for "author response", and another date for "author notification".

It's the first time I see this double wording. 
I suppose that "author notification" is when they communicate to authors if their papers have been accepted or not, but what does "author response" stand for?

Thanks
It has to be a conference with a rebuttal phase, where the authors can answer the main points raised by the reviewers, who in turn will be able to draw more conclusive remarks on the paper itself

see also here: http://www.cs.utexas.edu/users/mckinley/notes/blind.html