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.https://www.google.com/tagmanager
Pingdom RUM(Real User Monitoring) is a feature of the Pingdom website monitoring and performance testing service. RUM enables you to collect and analyse data on how real users are experiencing your website.https://www.pingdom.com/real-user-monitoring/