There is a property of language, called "compositionality". It means that in any sentence, you could replace a word with a phrase with the same meaning, and the meaning of the sentence would stay the same. Let's look at the following two sentences:
I ate a carrot.
I ate a crunchy orange vegetable.
The meaning of these two sentences stays the same, while the phrasing and style change. Today's Artificial Intelligence algorithms working with language could not really capture compositionality.
The multiplayer game you are about to play is built around this property of language. We hope that the data we collect would help us build better, more human-like natural language processing systems.
You will compete with other players in your ability to replace words with phrases that accurately represent the meaning of the word while still sounding naturally in context.
We did our best to make the game fun, but if it's not fun enough - know that you are helping science while playing.