"News Feed Ads", also called "Sponsored Stories", "Boosted Posts", typically exist on social media platforms that offer a steady stream of information updates ("news feed") in regulated formats (i.e. in similar sized small boxes with a uniform style). Those advertisements are intertwined with non-promoted news that the users are reading through. Those advertisements can be of any content, such as promoting a website, a fan page, an app, or a product.
Email marketing is the practice of nurturing leads and driving sales through email communications with your customers. Like social media, the goal is to remind users that you’re here and your product is waiting. Unlike social media, however, you can be a lot more aggressive with your sales techniques, as people expect that email marketing will contain offers, product announcements and calls to action.