Foursquare is the most popular location service app on the planet. I have been using it for a couple years now and very active. I use it for a variety of reasons, one being letting my friends and clients know of cool and interesting places to visit.
The ADVENTURER badge is received after you check into 10 different venues. I received this one at Walgreens in Aurora, CO.
The unlock text reads:
You’ve checked into 10 different venues! Now, how about inviting some friends into the mix? You can check out new spots together, share recommendations, and earn sweet BFF bonus points!