In the Year of the Boar and Jackie Robinson gives you some idea of Jackie Robinson's accomplishments (things he did that were great). But it might help your understanding of the story to know a little more about him
Robinson was the first black ball player to play in the white leagues. Initially he was hated for entering what many thought should be an all white sport. But Robinson was fearless. (Note the suffix "less" meaning "without")After Branch Rickey hired him in 1946, he ignored what people said to him on the field and played great baseball. But other players despised (really hated) him because of his color. The shortstop (You have to look it up. I don't know what this player does) and team captain Pee Wee Reese decided that was stupid. What mattered was that Robinson played great ball.
One day Reese went over and put his arm around Robinson. Robinson smiled back. From that day on the ice was broken (idiom meaning things start to change), and more players began to accept him. Attached is a picture of the two men and a memorial( Remember that word from Sadako and the Thousand Paper Cranes?) to their friendship. Sometimes one person makes a big difference.