Per Recode, Kurt Wagner breaks down the latest update to Twitter's privacy policy:

"The company already collects web browsing data when you visit third-party websites that use its API, which might mean a website that has 'embedded timelines or Tweet buttons' on it. And while Twitter previously stored that information for ten days, it now says it will store it for 30 days." Twitter will also display what "interests" it thinks you have, using the data collection to decide which ads and content to show you in your timeline. "Some of these interests are derived from your Twitter activity — like who you follow, and what accounts you engage with. But Twitter will also show you "interests from partners," or categories that advertisers have put you into based on data they collect off Twitter.It's all here: Click "Your Twitter data," down the left column.