A Potentially Unwanted Program (PUP)
is a very broad threat category which can encompass any number of different programs to include those which are benign as well as malicious. Thus, this type of detection does not always necessarily mean the file is malicious or a bad program. PUPs in and of themselves are not always bad...many are generally known, non-malicious but unwanted software usually containing Adware
with other free third-party software to include toolbars, add-ons/plug-ins and browser extensions. PUPs are considered unwanted because they can cause undesirable system performance or other problems and are sometimes installed without the user's consent since they are often included when downloading legitimate programs. PUPs may also be defined somewhat differently by various security vendors and may or may not be detected/removed based on that definition
. That fact adds to confusion and a lot of complaints from end users asking why a detection was not made on a particular file (program) they are having issues with.
Many programs, toolbars
come bundled with other free third-party software as a common practice by legitimate vendors
To learn more about PUPs and how you get them, please read: About those Toolbars and Add-ons - Potentially Unwanted Programs (PUPs)