Bitcoin is a digital or virtual currency that uses peer-to-peer technology to facilitate instant payments. Bitcoin is decentralized, meaning it is not subject to government or financial institution control.

The network is powered by blockchain technology, a distributed ledger enforced by a disparate network of computers. Bitcoin is unique in that there are a finite number of them: 21 million.

Bitcoins are created as a reward for a process known as mining. They can be exchanged for other currencies, products, and services.

As of February 2015, over 100,000 merchants and vendors accepted bitcoin as payment.

Bitcoin can be purchased through a digital marketplace, through which you can fund your account with your currency of choice, and place an order on the open market. Bitcoin transactions are then verified by network nodes through cryptography and recorded in a public dispersed ledger called a blockchain.

Bitcoin mining is the process by which bitcoins are created and transactions are verified. Miners are rewarded with bitcoins for verifying and committing transactions to the blockchain.

Mining requires significant effort and technology, so it is often done in pools, where many people work together to earn a block reward that is split among the group.

Is it worth investing $20 in Bitcoin? That depends on your goals and risk tolerance. Bitcoin is still a young and volatile market, so it may not be the best investment for those looking for stability.

However, for those willing to take on some risk, investing in Bitcoin could potentially offer high rewards.