Bitcoin system is an overlay network(there need not be a physical direct connection among nodes, but at the application level it appears to be connected in a peer-to-peer fashion) among nodes participating in it.
In a centralized system, a central authority for e.g bank, government manages(in PayPal, the managers) all the transactions, balances that are with or related to a user. But in bitcoin ideally, every node keeps a record of account information corresponding to each user with itself (in the form of blockchain) and update it time to time. Practically due to resource constraints only fully validating nodes keeps a track of entire blockchain.
The role of a miner in bitcoin is purely to accumulate the transactions at a single place and add it to the blockchain. To avoid centralization by a single miner this task is randomized so that every node gets a chance to add to the blockchain depending upon the computation power spent by the nodes.
1) PayPal is not peer to peer. You send money to the bank account of PayPal or they take it from you bank account. But if you send the money to someone, it's still on the back account of paypal until someton takes it. Paypal is a financial instituation that can decline payments (they did do that in the past). 2) Miners don't check the receiver and sender of a transaction. All, they do is putting valid transactions into a block. – ndsvw – 2018-01-09T12:05:25.500
Right. But for the end user, he just scans the paypal's code of the receiver and payment is done. Sender to receiver. So isn't this peer to peer? – user5155835 – 2018-01-09T12:10:59.043