Geocache Types:
I feel it is important to know and understand the different TYPES of caches and their icons. Looking at all the different types of caches on your app or on the GPSr can be overwhelming at first. It is also helpful to know this when narrowing down what you actually want to hunt for on your geocaching adventures.
Again, I pulled this information from the Official Geocaching website.
Traditional Geocache 
This is the original type of geocache and the most straightforward. These geocaches will be a container at the given coordinates. The size may vary, but at minimum, all of these geocaches will have a logbook. Larger containers may contain items for trade and trackables.
Mystery or Puzzle Caches
The “catch-all” of geocache types, this type may involve complicated puzzles that you will first need to solve to determine the correct coordinates. Mystery/Puzzle Caches often become the staging ground for new and unique geocaches that do not fit in another category.
Multi-Cache 
These geocaches involve two or more locations, with the final location being a physical container with a logbook inside. There are many variations, but typically once you’re at the first stage, you will receive a clue to the whereabouts of the second stage. The second stage will have a clue for the third, and so on.
EarthCache 
An EarthCache is a special geological location people can visit to learn about a unique feature of the Earth. EarthCache pages include a set of educational notes along with coordinates. Visitors to EarthCaches can see how our planet has been shaped by geological processes, how we manage its resources and how scientists gather evidence. Typically, to log an EarthCache, you will have to provide answers to questions by observing the geological location. For more information about EarthCaches visit http://www.earthcache.org/.
Letterbox Hybrid 
Letterboxing is another form of treasure hunting that uses clues instead of coordinates. In some cases, the letterbox owner has made their container both a letterbox and a geocache and posted its coordinates on Geocaching.com. These types of geocaches will contain a stamp that is meant to remain in the box and is used by letterboxers to record their visit. To read more about letterboxing, visit Letterboxing North America.
Event Cache 
An Event Cache is a gathering of local geocachers or geocaching organizations. The Event Cache page specifies a time for the event and provides coordinates to its location. After the event has ended, it is archived.
)Cache In Trash Out Event : CITO 
Cache In Trash Out is the environmental initiative supported by the geocaching community. The main aim of this program is to clean up and preserve the natural areas that we enjoy while geocaching. These events are larger gatherings of geocachers that focus on litter clean-up, removal of invasive species, planting trees and vegetation and trail building.
Mega-Event Cache 
A Mega-Event Cache is an Event Cache that is attended by 500+ people. Many Mega-Events offer geocachers a day of planned activities. There are often several days of additional activities surrounding a Mega-Event. These large events attract geocachers from all over the world and are often held annually.
Giga-Event Cache 
This is one of the rarest geocache types available. A Giga-Event Cache is an event that is attended by 5000+ people. These events are similar to Mega-Events and may include activities, could last several days and are usually held annually. Since Giga-Events are so rare, they attract geocachers from all over the world.
Wherigo™ Cache 
Wherigo is a toolset for creating and playing GPS-enabled adventures in the real world. By integrating a Wherigo experience, called a cartridge, with finding a geocache, the geocaching hunt can be an even richer experience. Among other uses, Wherigo allows geocachers to interact with physical and virtual elements such as objects or characters while still finding a physical geocache container. A Wherigo-enabled GPS device is required to play a cartridge. Learn more at Wherigo.com.
Geocaching HQ Geocache 
The Geocaching HQ Geocache is located at Geocaching HQ in Seattle, Washington. Geocachers interested in visiting HQ to log the geocache should make an appointment at least 48 hours in advance via hqvisits@geocaching.com. Appointments help us keep Geocaching HQ running smoothly. Visits are available Tuesday through Friday, from 2–3pm. For the ultimate HQ experience, we recommend scheduling your visit for Friday.
Lab Caches 
Welcome to Geocaching HQ Research & Development. A Lab Geocache is an experimental and extremely rare geocache type. These geocaches are a way for us to innovate and test—often at the molecular-level—new ideas to make geocaching even better. By finding a Lab Geocache, you’re helping shape the future of geocaching.
Grandfathered Cache Types
These are geocache types that are still available to find, but no longer available for creation on Geocaching.com. The reasons for why each of these types was retired varies.
Virtual Cache 
A Virtual Cache is about discovering a location rather than a container. The requirements for logging a Virtual Cache vary—you may be required to answer a question about the location, take a picture, complete a task, etc… In any case, you must visit the coordinates before you can post your log. Although many locations are interesting, a Virtual Cache should be out of the ordinary enough to warrant logging a visit.
Virtual caches are considered waymarks on Waymarking.com.
Webcam Cache 
These are geocaches that use existing web cameras that monitor various areas like parks or business complexes. The idea is to get yourself in front of the camera and save a screen capture from the website where the camera is displayed in order to log a find. New webcam geocaches can be found in the Web Camera category on Waymarking.com.
Project A.P.E. Cache 
In 2001, fourteen geocaches were placed in conjunction with 20th Century Fox to support the movie Planet of the Apes. Each geocache represented a fictional story in which scientists revealed an Alternative Primate Evolution (A.P.E.). These geocaches were made using specially marked ammo containers and contained an original prop from the movie. Only a few Project A.P.E. caches still exist today.