Ordinarily demos appear ahead of games' releases, but that's not the case with Bungie's sci-fi shooter Destiny. The game was released for PS4, Xbox One, PS3 and Xbox 360 back on September 9, and only now a demo has appeared.
The word trial might be better suited though, as Bungie lets you carry on with the main game, should you choose to acquire it, without losing your progression. The amount of data you must download also suggest that the developers hope is for people to continue playing once the free content ends, as the trial is roughly the same size as the main game (around 20GB for PS4/Xbox One and 9GB for PS3/360).
It's still unclear how much of the journey to "become legend" you get to enjoy before money needs to be spent, or if there is a level cap. That said, the trial should already be live on all four formats.