Bitcoins can be accepted as a means of payment for products sold or services provided. If you have a brick and mortar store, just display a sign saying “Bitcoin Accepted Here” and many of your customers may well take you up on it; the transactions can be handled with the requisite hardware terminal or wallet address through QR codes and touch screen apps. An online business can easily accept bitcoins by just adding this payment option to the others it offers, like credit cards, PayPal, etc. Online payments will require a Bitcoin merchant tool (an external processor like Coinbase or BitPay). 
Another interesting way (literally) to earn bitcoins is by lending them out, and being repaid in the currency. Lending can take three forms – direct lending to someone you know; through a website which facilitates peer-to-peer transactions, pairing borrowers and lenders; or depositing bitcoins in a virtual bank that offers a certain interest rate for Bitcoin accounts. Some such sites are Bitbond, BitLendingClub and BTCjam. Obviously, you should do due diligence on any third-party site.

A hard fork of a cryptocurrency is a change to the protocol that makes previously invalid blocks/transactions valid (or vice-versa). This requires all the nodes to upgrade to the latest version of the protocol software. In other words, a hard fork is a permanent divergence from the previous version of the blockchain, and nodes running previous versions will no longer be accepted by the newest version. This, in turn, creates a fork in the blockchain: one path follows the new, upgraded blockchain, and the other path continues along the old path.
Backtracking a bit, let's talk about "nodes." A node is a powerful computer that runs the bitcoin software and helps to keep bitcoin running by participating in the relay of information. Anyone can run a node, you just download the bitcoin software (free) and leave a certain port open (the drawback is that it consumes energy and storage space – the network at time of writing takes up about 145GB). Nodes spread bitcoin transactions around the network. One node will send information to a few nodes that it knows, who will relay the information to nodes that they know, etc. That way it ends up getting around the whole network pretty quickly.

Bitcoin mining is intentionally designed to be resource-intensive and difficult so that the number of blocks found each day by miners remains steady. Individual blocks must contain a proof of work to be considered valid. This proof of work is verified by other Bitcoin nodes each time they receive a block. Bitcoin uses the hashcash proof-of-work function.
Based in Austin, TX, Steven is the Executive Editor at CoinCentral. He’s interviewed industry heavyweights such as Wanchain President Dustin Byington, TechCrunch Editor-in-Chief Josh Constine, IOST CEO Jimmy Zhong, Celsius Network CEO Alex Mashinsky, and ICON co-founder Min Kim among others. Outside of his role at CoinCentral, Steven is a co-founder and CEO of Coin Clear, a mobile app that automates cryptocurrency investments. You can follow him on Twitter @TheRealBucci to read his “clever insights on the crypto industry.” His words, not ours.

Hardware wallets are by far the most secure kind of Bitcoin wallet, as they store Bitcoins on a physical piece of equipment, generally plugged into a computer via a USB port. They are all but immune to virus attacks and very few instances of Bitcoin theft have been reported. These devices are the only Bitcoin wallets which aren't free, and they often cost $100 to $200. 

Jump up ^ Mooney, Chris; Mufson, Steven (19 December 2017). "Why the bitcoin craze is using up so much energy". The Washington Post. Archived from the original on 9 January 2018. Retrieved 11 January 2018. several experts told The Washington Post that bitcoin probably uses as much as 1 to 4 gigawatts, or billion watts, of electricity, roughly the output of one to three nuclear reactors.
So that’s Bitcoin mining in a nutshell. It’s called mining because of the fact that this process helps “mine” new Bitcoins from the system. But if you think about it, the mining part is just a by-product of the transaction confirmation process. So the name is a bit misleading, since the main goal of mining is to maintain the ledger in a decentralized manner.
The buttons are used to confirm transactions. In order to send a transaction, you must physically press or hold buttons on the devices. This is a security feature. If a hacker were to access the hardware wallet somehow, the hacker still would not be able to send a TX without physical access to the buttons. Read more about this in TREZOR’s security philosophy.
Miehe still runs his original mine, a half-megawatt operation not far from the carwash. But his main job these days is managing hosting sites for other miners and connecting outsiders with insiders—and he’s OK with that. He sold off some of his bitcoin stack, just after Christmas. He’s still bullish on crypto, and on the basin’s long-term prospects. But he no longer has any appetite for the race for scale. Gone are the glory days when commercial miners could self-finance with their own stacks. Today, you need outside financing—debt—which, for Miehe, who now has two young children, would mean an unacceptable level of stress. “I’ve already done it,” he says. “My entire data center was built with bitcoin, from nothing. I’ve already won enough for what I was looking for out of mining.” He pauses. “The risk and reward is getting pretty great,” he says. “And I’m not sure I want to be on the front line of that battle.”
The blocks chain is secured by the miners. Miners secure the block by creating a hash that is created from the transactions in the block. This cryptographic hash is then added to the block. The next block of transactions will look to the previous block’s hash to verify it is legitimate. Then the miner will attempt to create a new block that contains current transactions and new hash before any other miner does.
Although BitFury claims to be producing chips whose performance is nearly identical to those used in the S9, the company has packaged them into a very different product. Called the BlockBox, it’s a complete bitcoin-mining data center that BitFury ships to customers in a storage container. Beijing’s Canaan Creative is still selling mining rigs to the public, but it offers only one product, the AvalonMiner 741, and it’s only half as powerful and slightly less efficient than the S9.

Bitcoins can be accepted as a means of payment for products sold or services provided. If you have a brick and mortar store, just display a sign saying “Bitcoin Accepted Here” and many of your customers may well take you up on it; the transactions can be handled with the requisite hardware terminal or wallet address through QR codes and touch screen apps. An online business can easily accept bitcoins by just adding this payment option to the others it offers, like credit cards, PayPal, etc. Online payments will require a Bitcoin merchant tool (an external processor like Coinbase or BitPay). 
Bitcoin solves the "double spending problem" of electronic currencies (in which digital assets can easily be copied and re-used) through an ingenious combination of cryptography and economic incentives. In electronic fiat currencies, this function is fulfilled by banks, which gives them control over the traditional system. With bitcoin, the integrity of the transactions is maintained by a distributed and open network, owned by no-one.
Though transaction fees are optional, miners can choose which transactions to process and prioritize those that pay higher fees.[67] Miners may choose transactions based on the fee paid relative to their storage size, not the absolute amount of money paid as a fee. These fees are generally measured in satoshis per byte (sat/b). The size of transactions is dependent on the number of inputs used to create the transaction, and the number of outputs.[3]:ch. 8
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