When you click on a folder and there is an option where it reads 'Add to archive' or 'Add to desktop .rar' does this mean your win zipping the files? I just need to make sure that I am doing the right thing, because when I win zipped a file it didn't make much of a difference to the size of the file.
You are zipping, but in anothe format. .zip is a native file which windows recognizes, but .rar would be recognized only with WinRAR. (from RAR labs).
Now, for your second question regarding the file sizes, you need to mention what type of compression you're aiming at. There's an option to compress to the highest. 7zip is another program, however if you are using 7zip or .rar, the recipient might not be able to open it in their computers unless they have these softwares installed in their systems. .Zip works well for all.