"Usage rights" give your brand partner the right to re-use your content after it goes live. The reason brands ask for usage rights is so, if they like the sponsorship, they can shorten it and then run it as a paid ad (e.g., a paid ad on YouTube, on TikTok, etc.). You're still the owner of the content! Usage rights are just a license for the brand to use your content for a set amount of time.
If you agree to usage rights, at the end of your campaign, you’ll be asked to send over a copy of your video to the brand, as well as a Spark code (for TikTok posts) or a partnership ad code (for Instagram).