Which of the following describes adware?

Adware refers specifically to software that automatically displays or downloads advertising material, often unwanted, when a user is online. The primary function of adware is to generate revenue for its developer by displaying ads to users, which can appear in various formats such as pop-up windows, banners, or even within the application interface itself.

This type of software can sometimes track user activity to tailor ads based on browsing habits, but its main characteristic is the display of advertisements. While adware might not always be malicious in the same way that some other types of malware are, it can be intrusive and negatively impact the user experience by overwhelming them with ads and potentially slowing down system performance.

In contrast, malicious software aimed at data theft focuses on compromising user data and privacy, while software that disrupts system performance can include various types of malware but isn't limited to adware. Software that manages project timelines is a specific type of productivity tool and doesn't fall under the category of adware at all. Hence, the definition that fits adware most accurately is its role in displaying advertisements.