ELI5: How does transacting on viewership data in alt currencies work?

Hoping someone can point me to a resource or is willing to explain how transacting in alt currencies works as it relates to advanced audience/demos, data, and measurement. Specifically focused on video, linear tv, streaming, and digital. Don't be afraid to brain-dump :)

And, if you work at a large ad agency, also curious about the following: - if you're at a holding company agency, how are you transacting across ott, digital video and linear? - if you're at an independent agency, are you transacting in alt currencies, specifically within video? how quickly are you adopting alternative currency and measurement solutions within video - Is this something you clear with the client? - What are the biggest headaches when using the different platforms that let you do this? can you do it independently?

TLDR: Explain to me like I'm 5- how does transacting on viewership data in alt currencies work (video, linear tv, streaming and digital media)?