What is the difference between Discount price and Product price campaign?

Discount price and Product price campaign have a distinct difference. Discount price immediately puts the product on sale

Discount price and Product price campaign have a distinct difference. Discount price is set under Products (PIM) > Products and immediately puts the product on sale, often marked with a red price.

As for a Product price campaign is set under Products (PIM) > Campaigns. A Product price campaign allows you to schedule a campaign and make multi-selection of products to be included in the campaign. You can choose a percentage on the regular price or the already discounted price on products.