JMeter is a Load-Testing Tool used for Performance Testing. A Performance Tester can record actions in a web browser or manually build a script which can then be run with hundreds or thousands of users.

JMeter can be used to create incredibly dynamic users and scenarios using its various elements. For instance, the CSV Data Set Config can be used to specify a set of users to log into a web application. The Regular Expression Extractor or the CSS/JQuery Extractor can be used to save session ids to be used in future requests. The JSR223 PreProcessor coupled to Groovy language can be used to create dynamic unique data for each user to be sent as part of a POST body.