"Last week we launched Local Updates to help you keep up with the places you love in your friends tab. Today, we’re introducing a new way for you to discover places when you’re looking for what to do next: Promoted Updates (including Promoted Specials!) in your Explore tab. It’s a great way to find out what’s happening at a local coffee shop, save money on your next clothing purchase, or just discover a store you’ve never been to before.
Promoted updates are just like the local updates that you see in your friends tab, except that businesses can pay to promote them in our Explore results. The update can be a money-saving special, an update on a new fashion line, or a photo of their latest dish. It works similar to ads on Google; there, if you search for ‘laptops,’ you’ll see an ad for an electronics website next to the results. In foursquare, if you do the same search in Explore you might see a promoted special about a weekend deal at a nearby computer store." – foursquare