Answer:
Achievement test or content test is designed to measure how much an individual has learned the skill or knowledge provided in a course, so achievement test aims to identify weaknesses and strength of an individual with respect to a specific taught course or textbook.
Aptitude test is a test designed to measure an individual’s specific skill, aptitude, or potential. It does not follow a certain course or textbook and does not need any preparation, unlike achievement test.
Achievement test makes decision about how much progress a person had in the past, while aptitude test makes decision or prediction on future by finding a person’s potentials.