Looking up another word for thoughtfulness in the dictionary will provide you with synonyms like attention to detail, kind-hearted, consideration, etc. It says thoughtfulness is the art of dealing with people sensitively and tactfully. It is the thoughtfulness that has led to new discoveries and the evolution of humankind.
Thoughtfulness makes the world a much better place.
Understanding is deeper than knowledge because many people know you, but very few understand you. People who understand others pick up emotional cues like non-verbal communication and body language and show sensitivity towards others and understand their perspectives. They also listen well to what people are saying and actively checking their understanding. Most people do not listen with the intent to understand; they listen with the intent to reply.
Understanding others does not mean that you have to agree with their feelings or point of view. Instead, it means that you recognize their point of view and accept that it is different from yours. Train yourself to ask the question, "How does this situation appear to the other person?" The goal here is not to be a mind reader or know with certainty what the other person is thinking. All you need to do is imagine what it would be like to be that person and make some reasonable guesses about what that person is thinking or feeling. Once you understand people well, it will be your second nature to be thoughtful and empathise with them.
- Urvashi Uniyal, The Doon Girls School Dehradun
References: The thoughtful me family encore; MBTI: understanding self and others