Paperless caching uses a GPX file to store the cache information. The ability to transfer single GPX files or create a Pocket Query (single GPX file with all the caches in it) is only available to Premium Members.
Smart phones like the iPhone, Android, Blackberry and Windows 7 all have inexpensive applications that displays all the cache information live if you are connected to the Internet (feature available to basic and premium members) or 'off line' by downloading your pocket queries (only available to premium members).
Personal Digital Assistants (PDA's) also accept the cache information but need to be running a program to view it. PDA's are devices that run the Windows mobile operating system (sometimes called Pocket PC) and Palm devices (running the Palm operating system). At the simplest level you can store the cache information as web pages and use the web browser to view them.
With a handheld GPS if you are not a premium member you can only get to see the cache coordinates and name and GC number. Using a third party software application may allow you to transfer more information. If you are a premium member then you can send a single cache to your device or do a Pocket Query of up to 1000 caches. The information you get is everything you see on the cache page; coordinates, name and GC number, description, hints, attributes and recent logs. You can also see whether there are any trackables logged into the cache. Smart phone users see all the information as long as you have an Internet connection. Without it you must download a Pocket Query first to use offline.
The cache page has links to allow you to download the information in several ways. The LOC Waypoint file only contains the cache name and coordinates. The GPX file contains all the cache information, name, coordinates, description, hint and logs. It also contains any additional waypoint such as clues or parking. The images from the cache page are only included with a Magellan GPS, not Garmin. Clicking the LOC or GPX file button only saves the file to your PC. If you use the Send to GPS button the file is saved directly to your GPS which needs to be connected to the PC. Send to PC or to GPS only saves the details of a single cache that you have open on the screen. If you want multiple caches you need to create a Pocket Query (PQ) which gives you a single GPX file but with full information about all the caches stored in it. A PQ can hold up to 1000 caches. How many caches a GPS receiver can hold various between the different models between 2000 and 12,000 (the Magellan eXplorist can store multiple PQ's so has a theoritical unlimited number).
To use the GPX and Send to GPS (GPX file) options and create Pocket Queries you need to be a premium member.
If you are using a Garmin or Magellan GPS that supports paperless geocaching you simply copy the GPX file directly to the device and it's ready to go. The GPX file can be a single cache from the cache page or a Pocket Query result of up to 1000 caches. With non-paperless GPS that can hold more basic information or a PDA (Windows or Palm) you need a program to open the GPX file and convert it to a format the PDA can read. The official smart phone geocaching applications can download the PQ directly from your geocaching.com account and use it offline.
Transferring a PQ to the GPS or phone is straightforward. If you want to process the cache information first, perhaps modifying a PQ to search for specific things then you can use a software application to do this for you, transferring the results to the GPS. If you want to put the PQ into a car sat nav like a TomTom or Pocket PC device then you'll need to convert it first with a suitable program.
The most popular programs for managing GPX files and PQ's are GSAK and Cachemate as they are both inexpensive. There are many others available and people do have their own preferences. The explanations shown in the 'how to' section below will use GSAK and Cachemate but the others work in much the same way.
The Geocaching Swiss Army Knife is a free program but has a 'nag' screen if you don't buy it! The current price is $US25. You load the PQ GPX file into GSAK and then convert it to whichever format you want. For example, you can export the file to use with Memory Map (Ordnance Survey digital maps), an HTML file to view in your PDA web browser, a database to use with Cachemate on the PDA or a file to load into a TomTom car sat nav.
Cachemate is a database application that runs on the Windows or Palm PDA and allows you to store all the cache information easily and also edit logs, manage trackables and even upload your logs directly to geocaching.com. Cachemate is currently $US10 to buy. Cachemate also has a GPS utility that lets you 'go to' the cache you select using the PDA GPS receiver.
EasyGPS - a more basic program for handling waypoints and GPX files. Free to use but you don't get maps. They are available on the Expert GPS product which you pay for.