Starseed Pilgrim is about discovery, to an extent which I have never seen before. It is a masterpiece.
The game does not tell you what its mechanics are, what your goal is, or what the narrative is - at least, not directly. Instead, it sets you free to discover whatever you can. Fortunately, you cannot lose, so every step, every success, and every failure, lets you learn something new that will bring you closer to answering the questions you have. If the idea of iteratively poking at an arcane puzzle appeals to you, you will likely love this game.
However, if you consider yourself impatient, it may not be for you. Starseed Pilgrim requires patience, as its discoveries take time to unravel bit by bit. If you don't like failing, that also might mean it's not for you. While the game isn't brutally difficult, you will definitely "fail" many times. Failing is an important part of its learning, as is being able to pick yourself up and try again.
There's not much more I can say about the game, as going deeper into the mechanics would spoil some of the discovery - the very crux of the experience! If you've read this and aren't put off, I heartily recommend that you give Starseed Pilgrim a try. You may fall in love with it as I have. But even if you don't, I can guarantee that it will be unlike anything you've ever played before; that in itself might be worth the price of admission. :)