Itch.io is rival competing against Steam for the independent game developers and publishers.
The cost is much lower than Steam which is intended to cover mainly web hosting costs. Organic growth has been rapid.
Itch.io has a loader just like Steam etc.
With a site like itch.io it’s possible to upload such games with a minimum price of $0. Effectively creating a nice landing page with fast downloads and screenshots. If there’s somebody out there who really likes the game then there’s nothing stopping them from supporting through a purchase.
Paypal is the only current processing system. Other providers may be added down the road.