What Computer Use is
A cloud desktop with a browser, what it's for, and what it isn't for.
osmos has a real computer: a Linux desktop in the cloud with Chrome, LibreOffice and a terminal. When a job needs a real logged-in browser, a native app, or anything visual, osmos uses it. Booking with airline points, filling in a form on a government site, pulling numbers out of a portal, checking availability on a site with no API.
It's the same machine every time, so logins you've done stay done. Files it produces land in your Files app.
When osmos uses it
osmos prefers its in-chat tools when they can do the job; the computer is for what those can't. You can also ask for it directly: "Use the desktop to...". Computer Use is rolling out gradually; if you don't see it yet, it's coming.