Apdex Levels group users into categories of satisfaction with the response time of web applications and services. These levels are defined as satisfied, tolerating or frustrated depending on their response time in comparison to a threshold.

Apdex Score is a measure of users' satisfaction with the response time of web applications or services. The Apdex Score is a value between 0 and 1, calculated based on three Apdex Score levels of user satisfaction: frustrated, tolerating, or satisfied.

Average Server Response Time is the average amount of time an application’s web server takes to return the results of a request to the user. It is affected by several factors including network bandwidth, number of users, and number and type of requests submitted.

Daily Active Users are the number of unique users of an application or platform that have interacted with it in a day. This metric is used to track daily user engagement. Daily Active Users includes both new users and existing users who have interacted with the application.

R&D Productivity is a performance measure of how much new revenue is associated with dollars invested into R&D within a technology company.