Cryptocurrencies are systems that allow for the secure payments of online transactions that are denominated in terms of a virtual "token," representing ledger entries internal to the system itself. "Crypto" refers to the fact that various encryption algorithms and cryptographic techniques, such as elliptical curve encryption, public-private key pairs, and hashing functions, are employed.
Apart from BTC, the altcoin market is also experiencing similar colossal dumps. All top-ten altcoins are presently in the red as massive selloffs dominate the market. As at press time, Ethereum, the second-ranked cryptocurrency by market capitalization is struggling to stay above $180, falling more than 14 percent. XRP is also another casualty of the market selloff, falling by more than 12 percent.
A cryptocurrency (or crypto currency) is a digital asset designed to work as a medium of exchange that uses strong cryptography to secure financial transactions, control the creation of additional units, and verify the transfer of assets.[1][2][3] Cryptocurrencies are a kind of alternative currency and digital currency (of which virtual currency is a subset). Cryptocurrencies use decentralized control as opposed to centralized digital currency and central banking systems.[4]
The proof-of-stake is a method of securing a cryptocurrency network and achieving distributed consensus through requesting users to show ownership of a certain amount of currency. It is different from proof-of-work systems that run difficult hashing algorithms to validate electronic transactions. The scheme is largely dependent on the coin, and there's currently no standard form of it. Some cryptocurrencies use a combined proof-of-work/proof-of-stake scheme.[16]

Bitcoin and many other cryptocurrencies are opening the doors to a new type of digital money, which we think has the potential to someday become a leading currency of the world. At the moment, even the oldest of cryptocurrencies are still maturing and only time will tell where this genius invention is heading. From what we can tell, there is plenty room for advancement. At the same time, Bitcoin has already revolutionized the digital world.

Basically, cryptocurrencies are entries about token in decentralized consensus-databases. They are called CRYPTOcurrencies because the consensus-keeping process is secured by strong cryptography. Cryptocurrencies are built on cryptography. They are not secured by people or by trust, but by math. It is more probable that an asteroid falls on your house than that a bitcoin address is compromised.
This is an important question to ask when choosing the best place to buy bitcoin. Yes, putting the words trustworthy bitcoin exchange and the best place to buy bitcoin in the same sentence seems like an oxymoron, especially when remembering the shiny days of MtGox (aka Empty-Gox). While the bitcoin protocol has never been hacked, many peripheral businesses have. Perhaps the best question to ask would be: which are the least secure bitcoin exchanges. Generally, those listed here are optimum and of good standing, but please proceed with caution. Remember never to leave more btc online than you can afford to loose.
In 2014, prices started at $770 and fell to $314 for the year.[32] In February 2014 the Mt. Gox exchange, the largest bitcoin exchange at the time, said that 850,000 bitcoins had been stolen from its customers, amounting to almost $500 million. Bitcoin's price fell by almost half, from $867 to $439 (a 49% drop). Prices remained low until late 2016.[citation needed]