The whole concept of Affinity Diagrams is to group similar ideas together so that they can be categorized and then worked upon. Categorizing requirements often help in coming up with new ones as well.
Affinity Diagrams are also known as KJ Diagram or Kawakita Diagram as it was invented by Jiro Kawakita.
Typically post it notes with ideas written on them are used so that they can be moved around as and when required.
RELATED LINKS
GROUP CREATIVITY TECHNIQUES
https://www.youtube.com/watch?v=HcD_PrN8mb8&list=PLLRADeJk4TCKnFYDMVUQ5WXoNzEh2EwGe
COLLECT REQUIREMENTS
https://www.youtube.com/watch?v=jAwx1t5HtHc&list=PLLRADeJk4TCKhCwJyVO5E0UuqMP18vSGs
LIST OF COMMON NAMES FOR YOUR PMP BRAIN DUMP
https://www.youtube.com/watch?v=nxjU2labmWY
SCOPE MANAGEMENT PLAYLIST
https://www.youtube.com/watch?v=S3UI2u2L1EQ&list=PLLRADeJk4TCKIr–TDiERNdEvqSIMeOBM
SCOPE MANAGEMENT FAQs PLAYLIST
https://www.youtube.com/watch?v=Zup8J-IGo_8&list=PLLRADeJk4TCLL5biuiHD3LJN8jpN2jinz
SHOP FOR PMP AT AMAZON INDIA
http://amzn.to/2xjhXlS