Mining

Mining is a record keeping service through the use of processing power. Miners keep the blockchain consistent, complete, and unalterable by repeatedly verifying and collecting newly broadcast transactions into a new group of transactions called a block. Each block contains a cryptographic hash of the previous block.

CPU
CPU mining is, as the name suggests, the process of mining on the CPU. It the considered lowest common denominator and often considered inefficient and unprofitable for Bitcoin and it's derivatives, despite advancements made in CPU technology as a whole, due to ASICs.

The original Bitcoin wallet was capable of CPU mining until the difficulty made it unprofitable. The 1% that are capable of profitability include CryptoNote-based currencies, such as Monero, or currencies based on or include the Proof-of-Stake algorithm. Most CPU miners for Bitcoin and early derivatives mine on the CPU only to secure network, knowing they won't get anything back.

GPU
GPU mining is second most common means of mining cryptocurrencies. It is more profitable to mine than CPUs but less profitable for any cryptocurrency mining dominated by ASICs. GPU mining may be the lowest common denominator for certain Bitcoin derivatives.

ASICs
ASICs (application-specific integrated circuit) are dedicated mining chips with efficiency magnitudes over CPUs or GPUs and getting better with every release, however the initial investment is more expensive than conventional means and usually only affordable to early adopters to Bitcoin mining or business. ASICs still consume a lot of power when grouped together, despite their increasing efficiency.

Rewards
Rewards is the incentive that drive mining. Rewards come in two flavors: new coins added into the network or fees. Most Bitcoin-derived currencies eventually stop generating new coins. The ones that do stop fallback onto fees to keep invective going while others that continue, such as Monero, return a bare minimum amount, known as emissions.

Pool mining
Pool mining (or "pools") is processing of sharing the hash power across all nodes in order to increase efficiency. It is the most common method mining, especially when dealing with ASICs. Pools generally have a set limit on when they'll release the funds to a miner's wallet.

Trust
Because pools are maintained by a central authority, a trust needs to be established in what is otherwise a trustless system. Ironically, sometimes the most professional looking pool may be the least trustworthy, but this is not always the case. Pools should be taken with a grain of salt for this reason but this should not discourage you from trying.