How to enable money withdrawal feature on our applications?

i am asking this question maybe this question is little theoretically but as a backend developer i am learning few things and this is something which i want to know how it works?

as there are lots of money earning app these days which allow user to participate and win real money in their wallet and after winning they withdraw their money into their own bank account directly .

so i want to know the whole procedure behind it how money flows from app to bank account of individual , is there any payment gateway required or is there any other techniques ?

any hint or thought would be very helpful Thank you!