Bitcoin 
Bitcoin (in the sense of currency – lower case) performs two functions:
- regarding the entire payment system and
- how to implement it using a digital token.
The bitcoin system was designed by Satoshi Nakamoto in such a way that direct transactions peer-to-peer (P2P) between users are possible, i.e. without the intermediation of the so-called a third party (e.g. a bank).
Manifest Satoshi Nakamoto
https://bitcoin.org/bitcoin.pdf
Bitcoin blockchain explorer
