Google-owned Youtube is obviously financed through advertising revenues, but the ads aren't popular with everyone. Therefore Google is implementing an alternative business model, where users can instead pay a fixed monthly fee to remove ads. According to the latest information, it will be launched at the end of October. Channel-owners like Pewdiepie has apparently no choice in the deal and are now asked to accept the new terms before October 22nd or their content will become "hidden".
From Youtube:
"To give fans more choice we will be launching a new ads-free version of YouTube, available to fans for a monthly fee. This service will create a new source of revenue over time that supplements your advertising revenue. That's why an overwhelming majority of our partners — representing over 95% of YouTube watchtime — have asked for and signed up for this service."