It provides your website for hackers. There are many ways to find you website vulnerabilities. Hackers use hacker scripts to find exploits automatically and they will manually test your website vulnerabilities. Mostly hacking scripts are written in PERL language - if you were aware of this hacking check your website traffic logs. If you have Enabled Error Reporting then hackers can find out all information about your website like extensions you have installed, Joomla settings, PHP scripts, server settings and more. So make your site more security, Error Reporting settings should be disabled.