Hi Huong! You would say somebody is active, when he/she is doing some physical activity, for example. Or you can say they lead an active lifestyle (exercising a lot). When somebody is an active church member, it means they are doing a lot for their church. The word "active" is used a lot. The word "proactive" on the other hand is not used that much. It means creating a situation. I would say you can remember it by memorizing the phrase "Being proactive is very creative". When you are creative, you don't wait for people to give you ideas, you just create those ideas yourself. When you are proactive you don't wait for something to happen, you just create a situation yourself.

Active means you're engage into something Ex. He was active in helping out in the church for the Christmas event. She actively listens to the teacher so she can get better scores on her exams. Proactive means you're doing something to prevent a situation from happening in the future. Ex. I am being proactive by not smoking so that I can lower my risk of getting lung cancer. The business chose a proactive approach to serve their clients better. Do you understand it better now?