What is the difference between `ash` and `sh` shell on Linux?

I am new to a lot of tools on Linux. A quick search did not help, I only got more about bash or sh, and searching for it somehow leans towards bash in the search results. There are quite a few different shell types out there, I have even seen zsh, thus I guess they are all forks from sh. There is already a question [What is the difference between using bash and sh to run a script?](https://unix.stackexchange.com/questions/270966/what-is-the-difference-between-using-bash-and-sh-to-run-a-script) that is similar: - but I could not find out what the "a" stands for in a shell - and this question is also not just about running a script, but the shell as such - since I can choose to take ash or sh for a docker container at hand. I remember ash would be more comfortable though still very slim, and I have forgotten why. What is the main difference between ash and sh? size, handling, ...? Base image was python:3-alpine, even the one with the latest tag (2022-07) has both /bin/ash and /bin/sh. There should be a reason why the two are there in the alpine image that is made to be the most compact of all. I call it with docker-compose -f docker-compose-develop.yaml run --rm MY_CONTAINER ash.