When you submit a paper, some conferences need you to make the two columns on the last page balance. That means the end of two columns on the last page must be on the same level. If you are using LATEX it is very easy to do.
You need to use a package called "balance":
If you haven't already installed balance package don't worry. When you run the latex it will automatically, after getting your permission of course, install the package for you. Then you can add "\balance" command anywhere in your document body. For example you can add it immediately after you begin the document:
For more information you may refer to this paper which contains more information about the "balance" package.