AdwCleaner used to be the market leader for ant-adware software but more recently companies like Scanguard have taken over thanks to their all round security package. Adwcleaner are solely for adware removal and not a full anti-virus. Software that automatically renders ads on your computer to generate revenue for it's author, known as Adware, is becoming a serious problem, so combatting it has become more paramount than ever before. Note, It's not particularly dangerous software, so don't be too worried, the main problem is that it can be a nuisance and in some cases slow down your system.
Adware does collect data from your PC but not in the way that malware (specifically trojans) does. They aren't collecting personal/confidential information from your files, but instead tend to collect meta data. They will then use the data for marketing, research and could even sell it. In simple terms they will usually collect data from your online activities and re-display ads that are more focused around your search results.
Adware cleaner tools have been around for some time, but are always evolving to keep up with the adware market. Today there are hundreds of solutions out there, so which one should you choose? You could opt for a solution that only focuses on adware, but we'd suggest looking at a package that will help remove, prevent and combat not only adware but spyware, malware, spam etc. in other words an all-in-one solution.
We'd always recommend looking for an antivirus package as these will more-than-likely include all the necessary tools to intercept and remove any kind of virus, from email spam to adware. So what should you look for in an antivirus package? The main and possibly most important feature to look out for is 'real-time protection'. This will allow the software to constantly monitor your PC and detect any nasty changes. This should keep you completetly protected.
The only problem with adware is that the end-user usually allows the adware on through accepting the installation of it via a 3rd party installation flow, without realising. A lot of antivirus software won't pick these up as suspicious because you've allowed it onto your PC, again don't be too worried as adware is generally harmful, just make sure to choose a package that allows for system scanning!
This is why a good adware removal program is essenial.