Within the campaign description, you should use a promotional message related to your campaign's aim: to drive influencer's attention on your product. Don't hesitate to use fun and catchy phrases, moodboards, videos, other images.
Within the product description, you should use a functional message that describes the product and its main functionalities (ingredient list, technical information, "how to use" description etc.). This section should be written in a way that allows it to be repurposed in various campaigns.
By default, if you don't fill in the optional campaign description, this information will be filled in automatically with the information in the product page associated with the campaign. When you put information against the campaign description, this will appear above the product description in the Free Store when you publish the campaign.
Don't hesitate to preview your campaign before publishing it! 👌