What is GPX?

The GPS exchange format: tracks, routes and waypoints, as XML. It's what watches, bike computers and handheld units produce, and what hiking and cycling apps import. Fixed fields, no room for extras, works everywhere.

What is GeoJSON?

The format web maps speak - points, lines and polygons as plain JSON, with arbitrary properties hung off each feature. Leaflet, Mapbox and every mapping library read it natively, which makes it the usual destination for map data that came from somewhere else.