What is the difference between CPQ product rules and price rules? When is each evaluated?

Product Rules automate product selection logic on the quote line editor:
- Validation: Blocks saving if an invalid product combination is selected. Evaluated on Save.
- Alert: Shows a warning but allows saving. Evaluated on Save.
- Selection: Automatically adds, removes, hides, or shows products based on other selections. Evaluated in the configurator as selections change.
- Filter: Dynamically filters the product catalog shown to the rep based on other quote fields. Evaluated when the product catalog is opened.
- Evaluation scope: Product/Quote (for bundle configurator) or Transaction (for the full quote). Conditions reference product fields; actions target product option fields.

Price Rules automate pricing logic — they inject calculated values into quote or quote line fields:
- Evaluated when the quote calculator runs (on quote save, product add/remove, or manual recalculate).
- Conditions: Define when the rule fires (based on quote field, quote line field, or summary variable values).
- Actions: Define what field gets updated and with what value (formula, lookup field, fixed value).
- Sort Order: Controls execution sequence. Lower sort order runs first. Critical when one rule's output feeds another rule's condition.