Bitcoin was described in a 2008 whitepaper by the pseudonymous Satoshi Nakamoto and went live in January 2009. It is secured by proof of work mining and has a hard cap of 21 million BTC, which makes it the reference "scarce" asset in crypto.
New bitcoin enter circulation as a mining reward that is cut in half roughly every four years (the halving). Bitcoin is still the largest crypto asset by market cap, and its share of the whole market is tracked as Bitcoin dominance.