'cd -' is implemented by the cd command using the OLDPWD environment variable. It works in all shells.

I did some digging and it turns out I had autopushd set. No wonder I didn't understand the usefulness of pushd/popd; I was already using them.

Also, by "cd -" I meant cd -[tab], cd -1, cd -2, etc.

Thanks! didnt know the tab feature.

cd is a shell built-in, not an external command. It has to be, since it changes the directory of the shell process, which can't be done by a child process. So shells do have to implement this specially.

Since no one has mentioned it and it would seem to be not well known, you can also cd to previous directory in bash:

cd ~-