PUA stands for Potentially Unwanted Applications and PUP stands for Potentially Unwanted Programs. They are basically the same. Both are pieces of software that enter the computer mostly without the consent of the computer user.
PUA/PUPs are also called adware. PUA and PUPs display unwanted advertisements, redirect your browser to unwanted website and unknown and unwanted search engines. PUA/PUPs are basically a grey line between legit and non-legit.
The behavior of PUA/PUPs are described in their EULA’s but no-one reads them, this behavior results in installations of software by simply selecting the next button.
In order to avoid installing such PUA/PUPs, you have to always install the main software by choosing the advanced/custom options. Do never click the Next of Quick install button, you might install software you do not want on your computer.
PUA/PUPs will slow down your computer and browser considerably, display loads of advertisements and report problems with your computer that are not “dangerous” or do not even exist.
What we see more and more are the System Optimizer applications, these applications report very simple problems as dangerous “problems”. For example a simple registry clean will be reported as a dangerous problem and should be fixed immediately. In order to solve these “problems” you need to buy a license to do so.
This kind of System Optimizer applications is one of many examples of what we call Potentially Unwanted Applications or Potentially Unwanted Programs.