There are several types of news in the game: new updates, social media activities, the start of a game event, and gifts. If you have an unread news item, an exclamation mark appears on the icon.
After you read the news, the exclamation mark goes away, but the message will remain on the news panel for a short while before disappearing. If you do not claim a gift during this time, the gift will go away when the message does. Usually, a news item disappears two days after it is read.