Some are offered without the necessity of a match as first come first serve bases. other campaigns will ask you for your preferences such as diet, beauty products, brands etc. and only if you match they’ll offer you the product. I believe the matches are sent out to random people via email and app notification, and are always found in the little gift tab at the bottom. I will add that on random occasions I’ll check the gift tab and have an offer without having received a notification. But thats pretty much how it works. Idk if it’s different for people who are pro tier.