So how exactly does the blockchain function? It’s actually a lot simpler than you think. Whenever a transaction is authorized and added to the ledger, it is replicated amongst all the nodes on the network. This means that every computer that is connected to a network which is using a blockchain has a copy of this ledger stored on their machine. Every time another transaction occurs, it is updated. Because these ledgers are simultaneously being kept on multiple machines, messing with or editing them is pretty much impossible. Furthermore, because it is being replicated and updated on all machines, there is no single point of failure, meaning if something happens to one ledger, there are thousands of others that can verify the data and omit the faulty one.
Full clients verify transactions directly by downloading a full copy of the blockchain (over 150 GB As of January 2018). They are the most secure and reliable way of using the network, as trust in external parties is not required. Full clients check the validity of mined blocks, preventing them from transacting on a chain that breaks or alters network rules. Because of its size and complexity, downloading and verifying the entire blockchain is not suitable for all computing devices.
An initial coin offering (ICO) is a controversial means of raising funds for a new cryptocurrency venture. An ICO may be used by startups with the intention of avoiding regulation. However, securities regulators in many jurisdictions, including in the U.S., and Canada have indicated that if a coin or token is an "investment contract" (e.g., under the Howey test, i.e., an investment of money with a reasonable expectation of profit based significantly on the entrepreneurial or managerial efforts of others), it is a security and is subject to securities regulation. In an ICO campaign, a percentage of the cryptocurrency (usually in the form of "tokens") is sold to early backers of the project in exchange for legal tender or other cryptocurrencies, often bitcoin or ether.
No one knows who the real owners behind btc-e are. Apparently the headquarters of the company are in Bulgaria and the support staff is more familiar with Russian then with English, but the rest is a mystery. The company operates a complicated deposit and withdrawal process that relays the money through several banks and payment processors before depositing them to your account. If you plan to deposit on BTC-E, make sure to follow their deposit instructions to the letter. Because the deposits go through a web of banks, tracking down a lost deposit is near to impossible.
In 1998, Wei Dai published a description of "b-money", characterized as an anonymous, distributed electronic cash system. Shortly thereafter, Nick Szabo described bit gold. Like bitcoin and other cryptocurrencies that would follow it, bit gold (not to be confused with the later gold-based exchange, BitGold) was described as an electronic currency system which required users to complete a proof of work function with solutions being cryptographically put together and published. A currency system based on a reusable proof of work was later created by Hal Finney who followed the work of Dai and Szabo.
Aside from the exchanges, you can also buy bitcoins on ebay and similar auction sites. Keep in mind that due to the possibility for chargebacks and fraud, bitcoin and other cryptocurrencies trade at a premium on ebay. Face to face meetups are another option to acquire bitcoins. Checklocalbitcoins.com for bitcoin sellers and buyers near your area. Always exercise caution when doing an offline exchange. Meet during the daytime and in places with a lot of people around. If possible, bring a friend.
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.
Once you bought your cryptocurrency, you need a way to store it. All major exchanges offer wallet services. But, while it might seem convenient, it’s best if you store your assets in an offline wallet on your hard drive, or even invest in a hardware wallet. This is the most secure way of storing your coins and it gives you full control over your assets.