Google Tag Manager is a tag management system (TMS) that allows you to quickly and easily update measurement codes and related code fragments collectively known as tags on your website or mobile app.
Internet Information Services (IIS) is an extensible web server software created by Microsoft for use with the Windows NT family.
Optimizely is an experimentation platform that helps developers build and run A/B tests on websites.
PHP is a general-purpose scripting language used for web development.