Twitter git hub. - css files

Dear all,

I want to use twitter github bootstrap files, when I downloded the files I got 4 CSS files namely (1) bootstrap (2) bootstrap.min (3) bootstrap-responsive (4) bootstrap-responsive.min

I am confused that in these files, that which file I can use to built my responsive design website, please explain me something on these 4 files what is the uses of these files.

please provide me some links where i can get the information.

below is the url from where you can download these files.

warm Regards