Conversely, many themes include the ability to choose how many columns a page will have. Each of these options is a page template that is available globally. To give your WordPress users this global option, you will need to create page templates for each option and give each a template name.
A quick, safe method for creating a new page template is to make a copy of page.php and give the new file a distinct filename. That way, you start off with the HTML structure of your other pages and you can edit the new file as needed.