As reported by Android Police, the service is powered by Mullvad VPN, which says it has a no-logging policy. It also uses the most recent WireGuard standard -- unlike existing protocols such as IPsec or OpenVPN -- for better encryption and faster speeds, which may give the service an advantage over other VPN offerings.
Mozilla has always maintained that its VPN services will be a paid-for feature -- presumably to circumnavigate claims that it would profit from user data. The Android app, which joins the Windows 10 app launched back in December, is available in the Play Store now and comes with a "limited-time beta price" of $5 a month. At this stage, it's only available to users in the US, but Mozilla says it'll roll out to other regions soon.