“Package Management” is a term you’ll hear tossed around as you venture into the catacombs of software development. This is not a reference to UPS’s main business, although the idea of boxes of stuff zipping through the mail is not unhelpful.
“Packages,” in this context, refer to pieces of software that are part of a larger software environment or application. They typically can’t stand alone, but are often ways of adding increased functionality or customization to whatever larger entity they pertain to. A package management system is simply a set of tools for finding, installing, and organizing all of the packages available to that entity.
To return to the UPS analogy, you can think of software packages as birthday presents. On their own they’re probably still nice, but they really need to show up at the right time and be the right item to have the full effect. UPS is the package management system. It takes the order from the customer (user), identifies the correct packages to send, and orchestrates their timely arrival to the correct address, all without any more work on your part.