Psychometric assessments are tools which are used to better understand a person's skill set, personality style, work style, or any other number of abilities. Sometimes these assessments are used to gauge if a person is improving in a particular area (such as with mental health assessments), or other times they're a one-time thing that can give employers some clues about whether or not a person will be a good fit in their organization.
When these types of assessments are often carefully constructed by psychologists to be as truthful as possible, there are some caveats! None of these types of tests are ever 100% accurate, but they can give us an idea of what a person can do. We still must use them very carefully to understand how they might not always truly reflect how a person might act in a given environment or situation.
For example, I once saw a manager twist the words from this kind of test to advocate for the candidate she wanted to hire, even though there were warnings that this candidate might be a poorer fit than the other candidates. So we have to be careful about not only the tests that we choose, but also how we read them and use them as well.
Additionally, some results should only be read by a qualified professional who is specially trained to understand them correctly, or else the person who took the assessment might be misunderstood.