Toy versus game
Also said as Software toy, Sandbox
A toy is something fun to handle with no goal attached. A game adds a goal and some way of failing at it. Many good games are a good toy with a game built around it.
If the bare action is not pleasant with no score attached, goals and rewards are just paint. Testing the toy first is one of the cheapest experiments in making games.
Say it
“Before any levels exist, I want a grey room with just the grappling hook in it. If people do not play with that for ten minutes, a goal will not save it.”
Where you’ve seen it
Will Wright said of SimCity, "I always wanted it to be much more open-ended, more of a toy." His publisher wanted a win or lose scenario, and to him it felt more like Lego.
Not to be confused with paidia and ludus
Toy and game describe the object. Paidia and ludus describe how someone is playing with it.