APT's are a type of attack that occur over a longer period of time and that is well organized by a skilled group of hackers, especially designed to use several attack-vectors and to stay unnoticed as long as possible.
Main motives are sabotage, espionage and stealing of sensitive data and intellectual property. APT's are often sponsored by large organizations or by nations('governments).
This is a highly sophisticated type of attack, well organized and well prepared, using different techniques and different attack vectors in combination with techniques that can bypass security measures and firewalls.
The main steps are: infiltration, scanning for vulnerabilities, establishing additional points of compromise, collecting the data and extracting the data to the hackers' devices or mostly the hackers' network. These hackers can be using any kind of malware or technique to achieve their goals.
Adware
Adware is unwanted software designed to throw advertisements up on your screen, most often within a web browser. Some security professionals view it as the forerunner of the modern-day PUP (potentially unwanted program).
Adware generates revenue for its developer by automatically displaying online advertisements in the user interface of the software or on a screen that pops up in the user’s face during the installation process. It's behaviour is quite obvious, you can't miss it: you're opening your browser and irritant pop-up screens appear or slide in from the side asking you to buy pills or warning you that your computer is infected and that you definitely need to install a certain scanner to clean out the malware.
Aside from annoying you, adware can also gather your personal information, track the websites you visit, or even record everything you type.
Adware comes mostly from downloaded software or through a browser vulnerability for which is no patch available yet. It can be difficult to find out where the adware came from because often it becomes active after several weeks or so.
Yearly millions of computers and mobile devices contract adware, mostly through installing free software or mobile apps.