Meaning: This sentence describes a situation where young people were engaged in a game where they threw an object for a dog to fetch and bring back.
Choice of Words: The word "children" refers to young people. "Played" means to take part in a game or activity for enjoyment. "Fetch" is a game where someone throws an object for a dog to fetch and bring back. "Dog" is a four-legged pet animal commonly kept by people.