What is the difference between nginx and nginx:alpine?

Question

My goal is to understand why is there a nginx image and also nginx:alpine image.

What I know:

1. nginx is larger, 52.79 MB.
2. nginx uses debian:bullseye-slim.
3. nginx:alpine is smaller, 9.51 MB.
4. nginx:alpine uses alpine.
5. both images can run static html just fine docker run -p 8080:80 -v ${PWD}:/usr/share/nginx/html nginx:alpine

I cannot wrap my head around why the default image uses debian:bullseye-slim rather than alpine.