concrete5 is built with PHP, a powerful scripting language. PHP can be set to display errors to help developers and site owners alike diagnose and fix problems. However, you may find yourself working on a site where it's preferable to hide error messages from average end-users. To accomplish this, PHP lets us show or hide non-critical errors as we specify. With concrete5, changing this configuration setting is as easy as flipping a toggle switch in the Dashboard's Debug page.
If you're having trouble with your site, it's recommended to make sure "Output error information to site users" is checked. The information provided in the error message can contain valuable information about fixing the problem.