The execution order of the test plan elements is -

Configuration elements : The Configuration Element allows us to declare variables that Samplers can utilise to access data.

Pre-processors : PreProcessors are JMeter elements that are used to perform actions prior to the execution of sampler queries in a test scenario.

Timers : A JMeter Timer is an inbuilt JMeter plug-in that can assist you in timing out your sampler requests. Many testers refer to this pause in requests as "think time," as it simulates the time spent by real users between steps in a real-world scenario.

Samplers : JMeter uses samplers to make several types of queries to a server. JMeter provides genuine queries to the web server under test using samplers. Except for Test Action, each sampler delivers one or maybe more sample results.

Post-processors : After the sampler, a Post-Processor element is executed and can be used for the post-condition response. If a Preprocessor is included in a test plan, it will be run after the response has been received. A Post-Processor is frequently used to extract information from a response to a specific action.

Assertions : In JMeter, assertions are used to verify the response to a request that you have given to the server. The assertion is the process of comparing the expected and actual results of a request at runtime.
Listeners- A listener is a component that displays the sample results. The output can be displayed in the form of a tree, tables, graphs, or simply sent to a log file.