GeoJSON is an open standard format designed for representing simple geographical features, along with their non-spatial attributes, based on JavaScript Object Notation - wikipedia 
# Using geojson
Geojson files are rendered automatically by github in order to allow you to view the data in a meaningful way in your GitHub repository. This also gives you the benefit of being able to visualise geojson files directly in GitHub Sites - github.com
# Howtos
- Example with OpenStreetMap layer
- as an eBook free to download or to read online
- Examples, but with MapBox layers as default
- Embedding GitHub Geojson
# Supported software
Here are some links to the best software I can find to use with geojson:
- MapBox - mapbox.com
- Creating and editing GeoJSON - geojson.io
- macwright.org
GeoJSON is supported by numerous mapping and GIS software packages, including OpenLayers, Leaflet (Leafletjs), MapServer, Geoforge software, GeoServer, GeoDjango (Django (Web framework)),Archived copy PointPlot, GDAL, Safe Software FME (Feature Manipulation Engine), and CartoDB.
It is also possible to use GeoJSON with PostGIS and Mapnik, both of which handle the format via the GDAL OGR conversion library. Bing Maps, Yahoo! and Google also support GeoJSON in their API services - wikipedia
# Specification
The features include points (therefore addresses and locations), line strings (therefore streets, highways and boundaries), polygons (countries, provinces, tracts of land), and multi-part collections of these types. GeoJSON features need not represent entities of the physical world only; mobile routing and navigation apps, for example, might describe their service coverage using GeoJSON.
* geojson.org
* geojson-spec - geojson.org
* h-geo microformats.org
{ "type": "FeatureCollection", "features": [ { "type": "Feature", "geometry": {"type": "Point", "coordinates": [102.0, 0.5]}, "properties": {"prop0": "value0"} }, { "type": "Feature", "geometry": { "type": "LineString", "coordinates": [ [102.0, 0.0], [103.0, 1.0], [104.0, 0.0], [105.0, 1.0] ] }, "properties": { "prop0": "value0", "prop1": 0.0 } }, { "type": "Feature", "geometry": { "type": "Polygon", "coordinates": [ [ [100.0, 0.0], [101.0, 0.0], [101.0, 1.0], [100.0, 1.0], [100.0, 0.0] ] ] }, "properties": { "prop0": "value0", "prop1": {"this": "that"} } } ] }
The GeoJSON format differs from other GIS standards in that it was written and is maintained not by a formal standards organization, but by an Internet working group of developers.