What is personality
The way a person responds in certain situations or their preferred way of behaving in a particular situation is their personality, naturally your personality affects your success in and suitability for any work role. For example, if you are outgoing and enjoy dealing with new people, you are likely to be more successful in sales and business development roles than a person who is shy and reserved. Similarly, if you tend to be methodical, systematic and to pay attention to details, you are likely to be more suitable for engineering roles than a person who pays less attention to structure and details.
Personality does not change significantly over time. It is valuable for an employer to know how you are likely to behave over the months and years you will be with their organisation— not just on the day that you are tested.