A standardized test is an assessment designed and conducted in a certain way to make sure all learners are taking the same assessment the same way.

It is effective when providing clear and objective image of learners' true academic level.

When looking at the bright side, standardized tests help educators to measure and compare learners' progress in achieving given objectives and to identify gaps and take actions to bridge them. They provide the raw materials for data analysts and researchers on a school level, district, country or worldwide to support educational or social researches.

Standardized tests could be misleading tool as well. They are at their worse when they become the only tool to measure learners' abilities or label learners. Not to mention that standardized tests mostly lead to teaching towards the tests and they can be biased or provide false insight of learners' progress depending on the different circumstances.

References: 

Oxford Learning:

https://oxfordlearning.com/pros-cons-of-standardized-tests/#:~:text=While%20there%20are%20advantages%20to,that%20can%20affect%20their%20performance.

Education Advanced:

https://www.educationadvanced.com/blog/standardized-tests-the-benefits-and-impacts-of-implementing-standardized

Britanica:

https://www.britannica.com/procon/standardized-tests-debate