How to make smooth screen effects

I want to achive smooth screen effects like in the video below! I do not want to use other sources, just script it by myself!

The issue is that I do not know how to do it as I am a beginner, so advices on what can I use to make it smooth as possible?

After that, you should include more details if you have any. Try to make your topic as descriptive as possible, so that it’s easier for people to help you!

Btw, I saw someone using math.noice for it but I did not quite get why did he use it!

Here is the video: