This number is called the mining difficulty. The mining difficulty expresses how much harder the current block is to generate compared to the first block. So a difficulty of means to generate the current block you have to do times more work than Satoshi Nakamoto had to do generating the first block.
To be fair, back then mining hardware and algorithms were a lot slower and less optimized. To keep blocks coming roughly every 10 minutes, the difficulty is adjusted using a shared formula every blocks.
The network tries to change it such that blocks at the current global network processing power take about 14 days. That’s why, when the network power rises, the difficulty rises as well. In the quest to further secure the network and earn more bitcoins, miners innovated on many fronts and for years now, CPU mining has been relatively futile.
You might mine for decades using your laptop without earning a single coin.
GPU About a year and a half after the network started, it was discovered that high end graphics cards were much more efficient at bitcoin mining and the landscape changed. The massively parallel nature of some GPUs allowed for a 50x to x increase in bitcoin mining power while using far less power per unit of work. With the successful launch of the Butterfly Labs FPGA ‘Single’, the bitcoin mining hardware landscape gave way to specially manufactured hardware dedicated to mining bitcoins.
That 5x improvement allowed the first large bitcoin mining farms to be constructed at an operational profit. The bitcoin mining industry was born. An ASIC is a chip designed specifically to do one thing and one thing only. An ASIC designed to mine bitcoins can only mine bitcoins and will only ever mine bitcoins.
The inflexibility of an ASIC is offset by the fact that it offers a x increase in hashing power while reducing power consumption compared to all the previous technologies. There is nothing to replace ASICs now or even in the immediate future. There will be stepwise refinement of the ASIC products and increases in efficiency, but nothing will offer the 50x to x increase in hashing power or 7x reduction in power usage that moves from previous technologies offered.
It is conceivable that an ASIC device purchased today would still be mining in two years if the device is power efficient enough and the cost of electricity does not exceed it’s output. Mining profitability is also dictated by the exchange rate, but under all circumstances the more power efficient the mining device, the more profitable it is.
If you want to try your luck at bitcoin mining then this Bitcoin miner is probably the best deal. Bitcoin Mining Software There are two basic ways to mine: On your own or as part of a Bitcoin mining pool or with Bitcoin cloud mining contracts and be sure to avoid Bitcoin cloud mining scams.