Until now, we have been treating the modules of swarm, whisper, and EVM as a black box, where we are only interested in how these modules interact, rather than what really happens inside them. However, to have a firm base for developing smart contracts, which we will eventually define and take up in Chapter 3, Hello World of Ethereum Smart Contract, we need to know the bare minimum internal workings of these modules. This will help us in tuning the smart contract code to make its performance better while running on the Ethereum blockchain.
Instead of downloading a file from a single server, with BitTorrent you download pieces of that file from other users across the globe who have the same file on their PC (hence peer-to-peer). The file or group of files you download is called a torrent, sharing those files is called seeding, and the group of people you download from is called a swarm. The more people connected to a given swarm, seeding a file, the faster you'll be able to download that file.
Note that we are also asked what SSH key to use. We can either use an existing one that we might have created previously or create a new one here. If we create a new SSH key we can download the according *.pem file to a safe place on our computer. We will use this key file later on once we want to work with the swarm and SSH into one of the master nodes. 2b1af7f3a8