From the publishers website:
When the game was invented and sold in a little woodgrain box, the author told us a required supplement was an Avalon Hill game called Outdoor Survival. This was a wilderness survival game that consisted of a hexagonal map system that players would travel around, trying to find their way back to civilization, all the while trying not to die of thirst or get eaten by bears. This game map was used as the first wilderness “hex-crawl” for what eventually became D&D. Later, Judges Guild took this to a whole new level with the Wilderlands series. For many years, hex crawling was just the way the game was played. This series brings that back, or supplements existing games that use that system of travel.
What a hex crawl is, literally, is a wilderness sandbox of areas, encounters and villages that players travel around in. It provides no story line, just hundreds of story hooks and possibilities.
These books provide a sub-setting in your own campaign world. They populate the world, and allow you to let your players explore that world, rather than just “travel 20 days” to the dungeon. Written by John Stater of NOD fame, each of these supplements details an area with a specific theme. Monster and NPC statistics are provided for each encounter area detailed.
each adventure comes in two varieties
either Pathfinder System Compatible Product or Swords & Wizardry