Malware is a harmful code that can infect any electronic device so that some of the functionalities may be changed, copied, or spoilt as per the attacker’s goal. A malware embedded in an advertisement with the intention of fraud/spam, so it cannot be spotted easily is called a malvertisement, therefore you must be careful while clicking such links.

Example:
You see an attractive offer like send message to 10 people and receive reward or spin the wheel and get on which ever offer the wheel stops and only to realise that it doesn’t work is kind of malware practice