It provides searchable list of command with human-readable descriptions.
Is there anything similar to this in Emacs?
Icicles provides what you describe.
And not only for
M-x but for anything that prompts for a command name.
And it provides the same thing for not just names of commands but everything else: faces, buffers, files, variables, functions, bookmarks -- you name it. It even provides completion of key sequences and menus/menu items.
And you can get additional information (complete doc string) about any completion candidates, on demand. And even without asking for complete doc on a candidate, you get a summary description of it in the mode line.
And you can progressively narrow the set of candidates by using multiple patterns to match
You can also try
counsel-M-x which comes with counsel package and uses
helm) as a backend.
If you are on emacs 25, there is the command
describe-symbol which can provide help for any face/variable/function and
ivy provides narrowing for that as well.