Play fair analysis
Play fairway analysis refers to a type of two dimensional mapping or map used in exploration in which regional trends in geology that are relevant to exploring for a particular play are depicted as polygons on the map. The purpose of this map is to visually suggest the main "fairway(s)" where the specific play is likely to be successful and additional exploration work at a smaller scale is warranted. A key part of the map is often what portions of the map are "off fairway" and don't warrant additional exploration. It is used in various types of exploration, including hydrocarbon and geothermal exploration.
Common phrasing is "play fairway", not "play fair". Fairways on the map sometimes look like fairways on a golf course.
The Department of Energy website has information on Play Fairway Analysis for geothermal energy:  The information below is written from the perspective of hydrocarbon exploration.
The map is typically created at regional scale (tens or hundreds of kilometers scale). There may be multiple play fairway maps in the same area with different maps for different time periods or play types. The play fairway map for a shale gas play might look very different than the map for a conventional fluvial play in the same area. Example inputs for a play fairway map for oil and gas exploration include regional structural trends (salt present or not) and gross depositional environments (shoreline sands or delta front sands or deepwater shale). Play fairway maps can contain different elements depending what information is available, needs of the user, and company specific definitions.
How Play Fairway Analysis Relates to Other Hydrocarbon Exploration Products
Gross deposition mapping (GDEs) are similar to play fairway analysis but focused specifically on the environments that deposited the rocks at the time period you are considering. Example polygons on a GDE map could be any depositional environment, including fluvial channels, deepwater slope channels, lake margin carbonates, salt-water marsh shales, etc.
Common risk segment mapping (CRS or CCRS) is also regional exploration mapping, but it is focused on mapping the level of exploration risk within the play. Often each parts of the CRS map are colored green, yellow, or red (a traffic light color scheme) to signify the level of risk. Red color suggests the play won't work in that polygon, yellow suggests uncertainty, and green says all the inputs for that type of exploration risk were positive for success.
How Play Fairway Maps Influence Exploration
The value of play fairway maps is often to show what is inside and outside the play fairway. "Off fairway" means the elements for that play to work are not present. This information is commonly used to plan future exploration work as a teams shifts to smaller scale exploration work. For example, this could mean shifting the exploration focus to a particular lease within the basin. Later work could be identifying prospects and drill exploration wells.