cmd+shift+a opens a command palette with every possible command in the IDE. It matches as you type the name of an action, and every action has a keybinding shown to the right (if it exists).
Every relevant button generally has keyboard shortcuts right on them.
And pressing cmd+e opens a list of gui interactions you've made so you can repeat them (things like focusing buffers, clicking on a file in the project file tree, etc.)
Basically, if you know cmd+shift+a, you're golden for learning commands and key shortcuts.
In comparison, emacs/vim are pretty awful. I've done a few tutorials of each and while I could have spent more time learning them, JetBrains makes it stupid easy to start learning the editor.
Alt-x does the very same in Emacs. Every available command with tab completion and with the keyboard shortcut listed. I think showing the shortcut is new.
If you are not familiar what a particular command does you can use C-h f <function-name> to open the help page.
I think Emacs is really easy to learn after you get a handle of the navigation keys. Which you might already be familiar with from shell.
