How to create bootable Ubuntu 20.04 on windows 10

I think so; a few weeks back, I was doing something on my Ubuntu 20.04. Suddenly my friend knocks on my door, and he was curiously peeking on my laptop screen. I asked what happen, Benhur?Benhur replied, what are you doing on your laptop, It is totally different from my laptop screen, and It fascinated me. Will you tell me what it is?