Well, that's clearly incorrect: software displaying unsolicited advertisements is called adware, and requires no spying at all.

> Spyware is a form of malware that hides on your device, monitors your activity, and steals sensitive information like bank details and passwords [0]

> Spyware is loosely defined as malicious software designed to enter your computer device, gather data about you, and forward it to a third-party without your consent. [1]

> Spyware is malicious software that secretly monitors your activity and collects sensitive information, like passwords, location data, or browsing habits, without your consent. [2][3]

0: https://www.malwarebytes.com/spyware

1: https://usa.kaspersky.com/resource-center/threats/spyware

2: https://us.norton.com/blog/malware/spyware

3: https://www.fortinet.com/resources/cyberglossary/spyware