https://en.wikipedia.org/wiki/360_deal
It’s a music deal that lets the labels take a cut of everything, including revenue streams artists used to have to themselves – shows, sponsorship deals, merchandising.
It used to be that if you bought, for example, a concert t-shirt or stickers or whatever (unsure if CDs/tapes were ever exempt) at the live performance that the artist got all or most of that. Artists could also control their own merchandising and aspects of their persona outside of the studio… personal appearances etc. but now the record labels ‘own’ them more completely. A terrible turn in general, and most labels demand a ‘360 deal or nothing’ to new artists.
“Merch” used to be the way artists made a lot of their income while on tour, since they didn’t make nearly as much from their album sales from an already unfair record-deal system; now they can’t even catch a fair break on tour.
Huge acts can negotiate better deals; the rest are stuck with unfair terms.
For Nebula/CuriosityStream? I only remember I bought a combo membership near Christmas the last two years – they usually offer a year-long subscription for like $11 USD around the holidays. Look out for those, I really like CuriosityStream and find it’s worth it.