Ever wonder how brands are able to follow visitors from their websites straight to the users’ Facebook pages?

Meet Facebook Exchange (FBX), a real-time ad auction platform that gathers information from user behavior on other websites for marketers to retarget their ads to the same users on Facebook. These ads used to appear on the right-hand side of the page, but they’ve recently made their way into the News Feed, where they’re mixed in with friends’ status updates and pictures.

So far, News Feed placement has led to a 197-percent increase in ROI compared to the original right-rail ads, according to the data compiled in this infographic by MDG Advertising. But space in the friend zone is limited, so marketers should see which post placement will work for their message and their goals before making the switch. “Right-rail Facebook Exchange ads are best for product ads pushing direct response,” writes the MDG team in a blog post, “while the News Feed ads are ideal for social media–centric promotions and content marketing.”

See more statistics, including a comparison of the costs and benefits of different types of ad retargeting on Facebook, in this infographic below. (Click through to the original blog post to access a larger version.)