Technically, it is all about removing the server from your application. The name literally tells you so. It is true that removing the server can offer some benefits in the scaling realm. In particular, it allows you to scale to 0 now that you no longer have to keep the process alive to serve requests.
Of course, that is not tradeoff free. Scaling to 0 brings you right back to the old problem of slow initialization once a request does come in, which was the primary driver for why we moved to hosting the server in the application in the first place.