What is KMZ?

A zipped KML, sometimes with icons and images bundled alongside. It's what Google Earth hands you when you export, and it's a single attachment rather than a folder, which is most of the appeal.

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.