Your web host provides you with the server space on which to run your site. Within many schools, your website will be hosted by your school. In other environments, you might need to arrange for your own web host by using a hosting company.
In selecting a web host, you need to be sure that they run software that meets or exceeds the recommended software versions.
Drupal is developed and tested extensively in an Apache environment. Drupal also runs on other web servers, including Microsoft IIS and Nginx.
Drupal 7 will run on PHP 5.2.5 or higher; however, PHP 5.3 is recommended. The Drupal 8 release will require PHP 5.3.10.