Bitcoin is a digital asset recorded on a public ledger maintained by a network of computers rather than a central bank or company. New coins are issued on a fixed schedule that halves roughly every four years, until 21 million exist.
It is used mainly as a speculative asset and a claimed store of value. In Australia it is generally treated as property for tax, so gains are subject to capital gains tax.
Why it matters
Bitcoin's price has historically moved with global liquidity and risk appetite: it tends to rise when money is cheap and investors are confident, and fall hard when they are not. Its volatility is several times that of the share market.
See the data: Bitcoin price.
General information, not advice.