Use AI to create a field based on another text field

Part 1) Yes definitely! I've done this in two different ways now.

Non-AI route - Use a simple if(contains()) formula.

With this style, you can just update it over time with addition lines. This would be the formula for your "Category" formula - Text field. 

If(
  Contains([Description], "invoice") or Contains([Description], "payment") or Contains([Description], "billing"),
    "Finance",

  Contains([Description], "schedule") or Contains([Description], "appointment") or Contains([Description], "meeting"),
    "Scheduling",

  Contains([Description], "error") or Contains([Description], "bug") or Contains([Description], "issue"),
    "Technical Support",

  Contains([Description], "training") or Contains([Description], "onboarding"),
    "Education",

  Contains([Description], "feedback") or Contains([Description], "survey"),
    "Customer Experience",

  "Uncategorized"
)