UPS driver release means that the UPS driver released the package either with a persons signature or even without a persons signature and left the package in a safe place.
The UPS Driver release also means that the UPS delivery driver decided to leave the package without getting a signature.
This is done a lot in residential areas seeing as during the day most people are at work.
This UPS driver release can also mean you either signed a signature release for your address allowing drivers to leave packages unattended, or the driver found a safe place to leave it.
If the package couldn't simply be left, the tracking status will show UPS InfoNotice was left.
Not all UPS packages will require a signature and if the package can be left in a safe location by the UPS driver then the UPS driver will leave the package and note on their device that they released the package.
Your package is likely somewhere near your house on your porch or could be hidden behind something on your porch.