Using Dynamic Lists

Hello

I would like more information on how to use Dynamic Lists. I read the Admin guide and I understand that you can associate criteria with the Dynamic list but I dont understand what that does or if it can solve my user request. I have a user request at my company where the users want some custom page 3 fields on a change order subclass for changes that affect Processes and Equipment. The 3 fields are Production Area, Process and Sub Process. At first I thought I would just create 3 unique fields for this. However the Users would like the system