The Universal Package Manager (UPM) is a tool designed to simplify package installation for developers, allowing users to import libraries and have them installed automatically. UPM uses the Overlay Filesystem technique to provide an independent cache for each user's projects, ensuring transparency and security. By leveraging content-addressable storage and pre-built wheels, UPM significantly reduces the time it takes to install packages, with a 40% decrease in installation time across all Always On repls.