Elegant Light Streak

I DID NOT design this composition, nor did I figure out how to do it on my own. I made this while following a tutorial on YouTube.

100% After Effects

Link to the tutorial:
https://www.youtube.com/watch?v=w-JG1n_Yeo8&list=PLwMQhFBsY_eP9cq8qFUwZeIF2gJYo7JmK&index=44&t=310s