CBT means Cognitive Behavioral Therapy. The simple idea is that what happens to us, what we think about it, how we feel, and what we do are connected. A situation may trigger an automatic thought, and that thought can push emotion in a strong direction.
The goal is not to erase emotion. The goal is to help emotion line up more closely with reality. If fear starts at 100 out of 100, the exercise is to examine the thought behind the fear and see whether a more balanced thought can bring that score down.
CBT works because some thoughts are incomplete, exaggerated, or distorted. A person may assume the worst, read someone else’s mind, blame themselves too strongly, or treat a possibility as if it is already a fact.
The exercise is simple: describe the situation, name the thought, name the emotion, score the emotion, question the thought, then create a more balanced thought. The power comes from repetition.
This page teaches by doing. It gives a little structure, asks a Socratic question, and then challenges you to rewrite the thought and score the emotion again.