Psychometric tests are designed to assess the cognitive abilities and personality traits of an individual. Knowing one’s own abilities, helps in knowing our own strengths and weaknesses which in turn help us in choosing the career/course most suited for us.
Aptitude is an innate quality or strength that helps one perform a task with certain competency. Another word for aptitude is ability.
Personality is the combination of characteristics or qualities that form an individual's distinctive character.