Hunters and Gatherers has its setting in the countryside near Carcassonne, before the establishment of its famed city walls. Like the original game it is based on, the objective of the game is to score points through judicious placement of terrain tiles and followers (colloquially referred to as meeples).
The King and Scout expansion to Carcassonne provides an expansion to this game, titled Scout.
After each tile is placed, the player may place one of their followers on the tile, which then claim ownership of a particular terrain feature: either a forest, river, or meadow. A player may place a follower only if no other followers have claimed the feature -- however, over time, it is possible that followers may share the same features due to placement of new tiles. Each player is only given seven followers; two huts [see below] and five ordinary followers.
In Hunters and Gatherers, however, there is a different type of follower: a fishing hut, of which each player is given two. Fishing huts may be placed on any river segment or lake, and claims the ownership of an entire system of rivers (ie. an entire body of water). Huts and ordinary followers do not influence each other's placement -- a player may have a hut and a follower on the same river, and opposing players are permitted to "share" rivers in this fashion.
The game is completed when the final tile is placed, and the player with the most points after a final round of scoring wins the game.
Rivers are considered complete when it either forms a closed loop or there is a lake or spring at both ends. They score one point for each segment (effectively one point per tile), plus one point for each fish in the lake(s) that may be at each end of the river.
Forests, which act analogously to cities in Carcassonne, are complete when they are surrounded on all sides with no room for expansion. Unlike Carcassonne, however, they score two points per segment -- hence it is possible for a single tile to contribute to four or more points in the scoring. Forests also award two additional points for each mushroom patch found therein. If the completed forest contains a gold nugget, the player completing the forest (not necessarily the player who scored for it) then draws a bonus tile from a special bonus pile and plays it, additionally scoring if any other rivers or forests are completed. Note that "chain reactions" are not permitted -- only one bonus tile may be drawn per turn. The player playing the bonus tile, as with normal tiles, may choose to place a follower or a hut on the tile.
The followers on these rivers and forests are removed and returned to the players' supplies. These followers may then be reused in the following turns.
At the end of the game, any followers on incomplete rivers or forests are removed -- incomplete rivers and forests (unlike Carcassonne) do not score for any player. It is at this time that meadows and huts are scored.
Huts award one point for each fish in the entire system, complete or not.
Meadows, which contain various animals, will score for the animals that are contained therein, regardless of whether the meadow is complete or not. There are three types of animals that contribute to the scoring: deer, aurochs, and mammoths, each worth two points. However, each tiger will negate the scoring of a single deer (but not aurochs or mammoths). Any tigers in excess will not adversely affect the scoring for a meadow. Tiles with burning grass, however, negates the effect of the tigers, allowing all deer to be scored on the field. Green discs are provided with the game to aid in this endeavor. There is also a special tile containing a shrine -- if a player has a follower on the shrine, only that player scores for the meadow, regardless of the number of followers contained within.
The fifth tile, the Shaman, allows a player to remove one of their own followers (not huts) each turn.