Spyware is software that secretly records what you do on your device. It’s not always dangerous and can be used for some legitimate purposes, but the majority of spyware is malicious. The main purpose for malicious spyware is to capture personal data such as passwords, banking credentials, credit card details etc. and send them to fraudsters via the internet. The purpose of anti-spyware software is to eliminate the chances of fraudsters getting hold of this kind of personal/private information.
How does spyware get onto your PC? The most common way is through downloading and installing un-verified/certified free