May 12, 2016 6:12 AM EDT

WHAT IS THE TRENDING BOX?

It’s the widget in the top right corner of the Facebook home page (when you first log in from a computer) that lists major news items relevant to your interests. It’s different from News Feed, the center column, which features posts from your friends.

WHO DECIDES WHAT’S IN IT?

A group of curators, who pick from a pool of popular stories surfaced by an algorithm. Unlike traditional news sites, which run staff mastheads and bylines, Facebook keeps their names private; the widget doesn’t indicate human involvement.

WHY ARE SOME PEOPLE UPSET?

Because some 63% of U.S. adult users get a portion of their news from Facebook, up from 47% in 2013. That gives the social network significant power–and has sparked more calls for transparency to ensure that that power is not being abused.

This appears in the May 23, 2016 issue of TIME.

Contact us at letters@time.com.

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