Chaff was the tribute from District 11 in the third Quarter Quell and the 45th Hunger Games. Chaff, along with Finnick, Mags, Johanna, Wiress, Beetee, Seeder, Woof and the Morphlings were a part of the rebellion and was instructed by Haymitch Abernathy to try his best to find Peeta and Katniss and make sure they both lived.
During the parade around the Capitol, Chaff and Seeder road around and after when all the tributes were together, Chaff gave Katniss a kiss on her lips which surprised Katniss and she pushed him away. Chaff and Haymitch begin to laugh at her reaction. During training, Chaff and Peeta became close and talked quite often during training and him along with all the other tributes that showed up to training had lunch together.
During Chaff's interview with Caesar Flickerman he states that President Snow could change the Quell if he wanted to but won't because he thinks it does not matter to anyone. After all the interviews were finished, Chaff along with the other victors joined hands as a act of rebellion.
Chaff was not seen much during the Games, and was probably hiding to stay alive and searching for Katniss as it was his mission to protect and rescue her so she could help the rebels defeat the Capitol.
Unfortunately he failed his mission as he could not locate either her or Peeta. He died at the end of the 75th Games, by Brutus, just as Katniss was rescued by the rebels.
Chaff was six feet tall, with dark skin, and an arm that ends with a stump because he lost his hand in the 45th Hunger Games. He was one of Haymitch's "Old Drinking Buddies." During the reaping recaps, Effie Trinket commented that "Chaff never could stay out of a fight," implying that he had volunteered as tribute. Chaff would have been in his mid to late forties when he died. He was killed at the very end of the 75th Games by Brutus at the free-for-all just minutes before Katniss Everdeen destroyed the force field surrounding the arena.
Chaff seems to be a troublemaker, as implied by Effie when she says, "Chaff never could stay out of a fight". Chaff loves to fight and is one of Haymitch's drinking buddies. Chaff jokes by kissing Katniss on her lips and laughing with Haymitch at her reaction. However, he does have his soft side such as when he is friendly and kind to Katniss and Peeta during the training session, backs Seeder up during her interview, and when he joins hands with the other victors at the end of the interviews without hesistation. Chaff is somewhat similar to Haymitch.