The letters A and T in the MBTI 16 personalities test refer to Assertive and Turbulent, respectively. Assertive individuals tend to have a healthy ego and report higher levels of life satisfaction compared to Turbulent individuals. They are confident and driven, comfortable taking charge and leading others.
The letters F and T in the MBTI test refer to Feeling and Thinking, respectively. Feeling individuals value and cherish their emotions and tend to follow their hearts and emotions in decision-making, while Thinking individuals make decisions based on pros and cons.