What is the exact functionality of UBER/ETSY/AIRBNB payment gateway?

Payment gateway for uber and aibnb.
How doe company provide payment protections for their customers
1-in terms of securing payment till service delivered (-releasing money when service is done? -after receiving feedback?
2-in terms of refunding money in case of unsatisfactory service.
Does airbnb get involved in refunding ? or Card processing companies being involved?