As mentioned in the previous lesson, the Bitcoin network is made up of computers running the Bitcoin software. These computers or “machines” are known as Bitcoin nodes.
Bitcoins nodes basically gossip. They love to talk to each other.
But instead of talking about recent drama from the Kardashians, they communicate about what’s going on around the network.
This is done by sending each other messages.
In Bitcoin’s case, each message contains information about a new transaction.
Nodes form a network by connecting and sharing transactions with one another.
This sharing of information (“transaction data”) is what allows all the computers on the network to stay up-to-date, which is pretty important if you want to run a digital currency on the internet.
Who is part of the Bitcoin network?
Any computer that is running a Bitcoin client software is part of the network.
Got an active Internet connection? Then you can join. Anybody can join the Bitcoin network!
Aside from an internet connection, you’ll just need to download and install the ソフトウェア (Bitcoin client) and let the application run on your computer all day long.
Once it’s up and running, the computer will be known as a Bitcoin “node” on the Bitcoin network.
There are no jocks or mean girls who will bully you and try to keep you out. Got a Bitcoin client software up and running on your computer? Welcome to the cool club. You now got node status yo.
In computer geek lingo, a “client” is a piece of hardware or software that connects to a server.
For example, an internet browser like Google Chrome or Apple Safari is a “client” since it connects to a website’s server to request its content
In the context of Bitcoin, a client is a software that connects to other clients in a peer-to-peer manner.
Because all these clients talk to each other, they form a network where each client is a node. There is no Bitcoin “server” for Bitcoin clients to connect to. Every Bitcoin client is, at the same, a server also.
To avoid confusion, this is why the term “node” is typically used in place of “client”.
The Bitcoin network is just a bunch of connected nodes from all over the globe. And there are over 15,000 of them!
Here’s a map showing the geographical distribution of Bitcoin nodes:
When you read Bitcoin (and other cryptocurrencies) described as being “managed by peer-to-peer networks of computers running software,” this is what they mean.
Think of the Bitcoin network as a leaderless network of independent computers (“nodes”) that operate autonomously based on the Bitcoin software.
English 
Japanese