Before Atlas, there were cookies, tiny fistfuls of data requested by a website and stored on a user’s computer. They carry information either from site session to the next or from one website to another. They are trail blazes, mementos, website digital inscriptions that say, “X was here.”

But cookies crumble when an Internet user switches from his business laptop to his smartphone, a public hotel desktop, or a friend’s tablet. Cookies only work per computer.

Then, and only then, came Atlas, a data-sharing advertisement platform from the world’s largest treasure trove of marketing and demographic information: Facebook.

The Five W’s of Facebook Atlas

Who: Facebook. Online social networking site, founded and chaired by controversial public figure mark Zuckerberg. Initial Public Offering (IPO) held trading volume record at 460 million shares. In-house terminology includes “poke,” “like,” “lolz,” and “defriend.”

What: Advertisement serving and tracking platform. The purpose of Atlas is that an Internet user would see contextual ads no matter which device she uses to access the Web. Considering that some experts believe each Internet user will connect via five personal devices by 2020, Atlas comes not a day too early.

Why: Because in the fiscal second-quarter of 2013, Facebook reported advertisement revenue of $2.7 billion. Ads are big business, and the more knowledge that Facebook has about clicks, sites, conversions and close-outs, the more effective ads will be.

When: Facebook re-launched Atlas in September 2014. It bought Atlas from Microsoft in 2013 for a rumored $100 million.

Where: Atlas can track user data across almost the entire World Wide Web.

Why Facebook Atlas Makes Marketers Salivate

Until now, Facebook and its marketing affiliates have used cookies to track the actions of users across different websites. This information is used to personalize each user’s marketing experience in what Facebook calls “people-based marketing.” Atlas will do the same, but it can do so across different devices. This is done using Google and Apple “advertising identifiers.”

Atlas can even match online users with their offline purchases. The process is simple. Say Suave gives Facebook a roster of Suave shampoo users by name. Facebook compares this list with its list of Facebook users who have seen or clicked on Suave ads. Facebook might give Suave percentage conversions, buying patterns and other macro-metrics, but it promises that cross-device data will not leave Facebook’s walls. Individual identities will not be revealed.

Facebook plans to establish Atlas as an ad-purchasing platform in the not-too-distant future. Needless to say, Atlas should already be on your Social Media Strategy radar.