Working of configuration elements is quitesimilar to those of samplers.However, it does not send requests but it allows you to modify the requests made by the samplers.
It is a simple element where you can collects the corporate configuration values of all samplers like webserver's hostname or database url etc.
A configuration element is accessible from only inside the branch where you place the element.
Given below is the list of some of the most commonly used configuration elements provided by JMeter:
The following image shows how you can add a configuration element to your test plan.