PUP = Potentially Unwanted Program.
Meaning, software that you may want. Or you may not.
This includes a broad range of software. Some toolbars, commercial (not malicious) keyloggers, much more. A good example is many tools from Nirsoft.
A good metaphor for PUP is a kitchen knife....a tool that can be useful and good, when used as intended, for cutting food. But it can also be deadly,when used with bad intentions, like for cutting humans.
