The Top-Rated Articles list that appears on the Homepage is designed to show which are the most voted-for articles, based on visitor feedback.
Voting for an article is based on visitors giving it a thumbs-up, or a thumbs-down vote, depending on whether they like it or not. More thumb-up votes means people generally like the article, whereas more thumbs-down votes an article gets means that people typically don't like the content.
These voting options appear at the top of the article page and are only available to users that have logged into the system (anonymous users are not able to vote - they must register before doing so).
Note that Content Editors can use this information as a way of tracking which articles visitors prefer, which can help guide content and design choices for other articles.
Seeing a list of Top-Rated articles is often helpful to see what other people like reading, since this may also be of interest to you, so having this list that shows the most popular articles is a convenient way to access those articles.
Top-Rated articles will only be shown in this list if they are marked as "Published" and also only listed if the current user is allowed to view the article, based on User Groups settings they have been assigned match the Groups assigned to the article's category.
This list will automatically populate as articles start to receive visitor votes. The maximum number of articles appearing in this list is also controlled by Admin Settings, including an option to specify this list is not shown, if desired.