Geocaching glossary

A worldwide treasure hunt played with GPS: containers are hidden all over, and their coordinates published online. The game began in May 2000, three days after the deliberate degradation of the civilian GPS signal was switched off.

The container itself, and by extension its online listing. It holds a logbook at the very least, sometimes items to swap. Also called a geocache.

The notebook inside the container. Writing your username and the date is the only proof of a visit that counts: an online log without a signature can be deleted by the owner.

The account posted online after a visit. It can be a Found it, a Did Not Find, a note, or a maintenance report.

The position of the cache, in degrees and decimal minutes: N 48° 51.402 E 002° 17.735. That is the format geocaching.com uses, not the decimal format of online maps.

The two ratings of a cache, 1 to 5 in half-point steps. Difficulty is what the search or puzzle costs, terrain is what the approach costs. A T5 needs special gear: rope, boat, diving.

Ground Zero, the exact point the coordinates give. GPS turns unreliable there under trees or between buildings, and that is where the real search begins.

A passer-by who knows nothing about the game. The word comes from Harry Potter. You "watch out for muggles" when retrieving a cache: being seen invites curiosity, and curiosity makes containers disappear.

First, Second and Third To Find: the first three to sign the logbook after publication. No official reward comes with it, which does not stop some from watching for notifications to set off within the hour.

Did Not Find: the log you file when you leave empty-handed. Several DNFs in a row alert the owner, and that is often how a missing cache comes to light.

Thanks For The Cache, the most common sign-off in logs. Owners generally prefer two sentences about the walk to those four letters.

Took Nothing, Left Nothing. Used when you sign the logbook without touching the swap items.

Cache In, Trash Out: carry a bag and pick up the litter you come across. The idea became an event type of its own, dedicated to cleaning up a site.

A photo or hint that gives away the hiding place. Owners can ask for one to be removed, and logs rarely carry any out of consideration for the next finders.

Bring Your Own Pen. The note appears on caches too small to hold one, which is almost every micro.

A container found and taken, emptied or destroyed by someone outside the game. The owner replaces it, or archives it.

The pictograms on a listing: wheelchair accessible, done at night, dogs allowed, parking nearby, length of the walk. They can be filtered on in searches.

The simplest and most common form: the container is at the posted coordinates. Close to two thirds of the caches in the world.

At least two stages: the first gives a clue or coordinates leading to the next, and so on until the final container, the only one with a logbook.

The posted coordinates are only a reference point, within two miles of the real cache. You must solve a puzzle to get the right ones. The hardest caches in the game are almost always mysteries.

No container and no logbook: it leads to a notable geological site and is logged by observing, then sending your answers to the owner. The type is overseen by the Geological Society of America.

A gathering of geocachers, listed like a cache and logged like one. It can be six people in a café or several thousand over a weekend.

A crossing of geocaching and British letterboxing: the container holds a stamp, and is often found by following written directions rather than coordinates.

A cartridge is loaded onto the device before setting off: it triggers dialogue, items and puzzles as you reach certain positions. The player follows a story instead of coordinates.

No container: you log it by answering a question asked on site or sending a photo. The type was closed in 2005, then reopened sparingly in waves of rewards.

A series of five stages played from a dedicated app, each validated by an answer found on site. There is no container, and the stages count separately.

A magnetic cylinder about a centimetre long, whose logbook is a strip unrolled with tweezers. Officially geocaching.com does not list this size and files it under micro.

Up to the size of a film canister. Holds the logbook and nothing else, hence the BYOP note on many listings.

About the size of a sandwich box. The logbook fits, along with a few small swap items.

The ammo can or the plastic box of a litre and up. This is the size that allows real swapping and that hosts trackables.

The geocacher container of reference: watertight, sturdy, indestructible. Many caches placed in the early 2000s are still going thanks to it.

A clear plastic tube, often a bottle preform, capped and hung in vegetation. Cheap, watertight, and nearly invisible once in place.

Any item carrying a unique tracking code that moves from cache to cache. Every move is logged online, and the journey can be read on a map.

A metal tag stamped with a code, attached to any object. Owners often set it a goal: reach a country, a summit. Some have passed a hundred thousand kilometres.

An engraved metal coin, minted by a geocacher or for an event, carrying a tracking code. Many are limited runs, which makes them collectibles as much as travellers.

Logging a trackable's code without taking it. The owner's counter goes up, the item stays where it is. That is what happens at an event, where dozens of trackables circulate.

The two moves that make a trackable travel: you retrieve it from one cache and drop it in another. Letting one sleep in a drawer for months is the community complaint heard most often.

A volunteer geocacher in charge of a region: they check the distance to neighbouring caches, the permissions and compliance with the guidelines, then publish the listing or return it. Their name appears in the publish log.

The one who placed the cache and maintains it: replacing a soaked logbook, checking after a DNF, archiving when they give up. Written CO, for cache owner.

The log that tells the owner a cache needs looking after. The listing then carries an icon until they declare the maintenance done. With no response, a reviewer eventually disables then archives it.

The paid geocaching.com membership. It unlocks member-only caches, advanced searches and favourite points. The basic account stays free and opens the vast majority of caches.

A premium member earns one per ten finds, and can only give each one once. The percentage shown on a listing is the best public indicator of a cache quality.

A badge awarded automatically for a first find in a country or region, or during a seasonal promotion. It is earned once and stays on the profile.

A mystery whose puzzle is a condition to meet: find a cache every day of a month, fill the D/T grid, visit fifty counties. You only log it once the condition is met.

The geocaching.com publishing rules: a minimum of 161 metres between two physical caches, permission from the landowner, nothing buried, nothing commercial. They are what a reviewer refers to.