Choose what happens when an article is clicked on. Either Show Article Content if a url is provided or Open Article Site inside a modal, using the content from the article formatted according to a predefined template.
Open Site in
This option it's only available when for action link you select Open Article Site. You choose whether pressing a news item with a link will open this link on a New Window, the Same Window or a Modal (pop-up window) on the page.
Links pointing to external sources might be blocked when using the modal, since the content is displayed inside an iframe. Links pointing to unsecure connections (using http:// instead of https://) will be blocked by SharePoint Online when using the modal.