Using in an Entry
All current Pricing Rules show up as checkboxes. Whatever you tick creates a relationship between the entry and the products, so you can list them in your templates using the plugin's custom variable.
Removed Rules
If a Pricing Rule you'd ticked earlier is later deleted in Commerce, the field flags it. You'll see a note telling you the stale selection will drop off the next time the entry is saved, so nothing lingers quietly in the background.
Use Cases
Special Offers Page
Say a client wants a Special Offers page that only shows curated products matching certain pricing rules, rather than everything. See example
Offer Categories
Say a client wants Special Offer Categories: July Offers, Autumn Offers, and so on.