From time-to-time, geocaching.com will announce special events and souvenirs related to the history of geocaching. Today (Sunday, 10/12/14) was one of those days.
If you fulfill the requirements, then GC will send an award or a souvenir to commemorate the day.
We spent the weekend down at the gulf, so the Earthcache we visited was at Little Lagoon. We had to read about different kinds of lagoons, observe Little Lagoon, and decide which type it is. We identified the different animals living around the lagoon, too. A very quick and simple Earthcache, we had all the questions answered plus a new souvenir in a few minutes.