I had a bit of a "Tyrel you know nothing" moment today with some commandline tooling.
I have been an avid user of ZSH for a decade now, but recently I tried to swap to fish shell. Along the years, I've maintained a lot of different iterations of dotfiles, and shell aliases/functions. I was talking to a friend  about updating from exa to eza and then noticed I didn't have my aliases loaded, so I was still using ls directly, as I have alias ls="exa -lhFgxUm --git --time-style long-iso --group-directories-first" in my .shell_aliases file.
I did this by showing the following output:
$ which ls /usr/bin/ls
Because I expected it to show me which alias was being pointed to by ls.
My friend pointed out that "Which doesn't show aliases, it only points to files" to which I replied along the lines of "What? No way, I've used which to show me aliases and functions loads of times."
And promptly sent a screenshot of my system NOT showing that for other aliases I have set up. Things then got conversational and me being confused, to the point of me questioning if "Had I ever successfully done that? Maybe my macbook is set up differrently" and went and grabbed that.
Friend then looked at the man page for which, and noticed that there's the --read-alias and --read-functions flags on which, and I didn't have those set. I then swapped over to bash "Maybe it's a bash thing only? I'm using Fish".
Nope, still nothing! Then went to google, and it turns out that ZSH is what has this setup by default. Thank you "Althorion" from Stackoverflow for settling my "Yes you've done this before" confusion.
It turns out that ZSH's which is equivalent to the ZSH shell built-in whence -c which shows aliases and functions.
After running /usr/bin/zsh and sourcing my aliases (I don't have a zshrc file anymore, I need to set that back up), I was able to settle my fears and prove to myself that I wasn't making things up. There is a which which shows you which aliases you have set up, which is default for ZSH.
$ which ls ls: aliased to exa -lhFgxUm --git --time-style long-iso --group-directories-first