Beyond opening apps and answering about your screen, Jarvis can take actions for you. This is the newest, least finished part, so here is the honest picture.

What works today

Drive a real browser: log in once on your own profile, then ask Jarvis to navigate, fill, and click.
One-shot actions in the app you are using: move, click, type, and send a keyboard shortcut.
Look at your screen and answer questions about it.

What does not work yet

Full hands-off control of every native Mac app is on the roadmap, not shipping.
Today it is strongest in the browser and for single, well-defined actions.