The purpose of this demonstration is to isolate the problem preventing an engine from starting. The video explains how we can tell the battery is ok (because it is able to power a motor that rotates the engine) suggesting the problem lies in ignition and/or fuelling mixture. The requirements of internal combustion are:
Fuel (petrol or diesel)
Air (oxygen)
Ignition (spark on petrol engines, glow plugs and compression on diesels)
Mixture (of the fuel and air, in correct proportions)
Compression (of the fuel/air mixture)
Engine rotation causing compression, either by push starting, starter motor or engine already running
Compression almost always fails during operation (e.g. blown gasket). Mixture usually fails slowly, due to lack of maintenance, or if the car has not been driven recently. Air is available unless blocked. The video shows how electrical supply can be confirmed (using dash lights) suggesting that ignition is possible, and further, how to confirm engine rotation and by implication, battery health.
3gp version for mobile/cell phones. More details on the wiki.