Bitcoin, being the first cryptocurrency ever created, could be considered a father of cryptocurrencies. It also usually is an entrance gate to their world. It was created in 2009 the moment an individual or a group of individuals, signed as Satoshi Nakamoto, placed a description of the site function principles on the internet.
Their intention probably was to start a revolution in the world of money through creation of money that cannot be influenced, forged and otherwise manipulated by the author, an individual, a group or government. Also, account blocking and inflation, would not be possible. The fundamental basis of the Bitcoin site is decentralization. No central control point exists in a decentralized site. This quality is ensured by the fact that the site is distributed. The Bitcoin site can be described as a peer-to-peer site that uses asymmetric encryption.
The used algorithm is called SHA-256 and was created by NSA organization in the way, that it cannot be deciphered by any now known means. The number of mineable units is unchangeable and predefined in the source code. Approximately in 2140 all units will be extracted, although clear majority will be extracted already in 2030.
An economical system called proof-of-work is also a part of Bitcoin site. In practise it means, that the value is based on computing power and transactions are confirmed by so-called mining operators. They are rewarded for this in the form of fees from users, who are requesting the transaction confirmations. This economical system is used in most cryptocurrencies, them being derivates of Bitcoin which means that their source code is a slightly amended copy of Bitcoin’s.
During its existence, there were various updates in the Bitcoin site. The most significant is SegWit update, which is an upgrade, that divides signature data from transactions as such. It brings advantages like an increase of the block capacity. If, however, SegWit is not activated by November 2017, one is not going to be able to activate it.