This handbook is a guide to ordinal theory. Ordinal theory concerns itself with satoshis, giving them individual identities and allowing them to be tracked, transferred, and imbued with meaning.
Satoshis, not bitcoin, are the atomic, native currency of the Bitcoin network. One bitcoin can be sub-divided into 100,000,000 satoshis, but no further.
Ordinal theory does not require a sidechain or token aside from Bitcoin, and can be used without any changes to the Bitcoin network. It works right now.
Ordinal theory imbues satoshis with numismatic value, allowing them to be collected and traded as curios.
Individual satoshis can be inscribed with arbitrary content, creating unique Bitcoin-native digital artifacts that can be held in Bitcoin wallets and transferred using Bitcoin transactions. Inscriptions are as durable, immutable, secure, and decentralized as Bitcoin itself.
Other, more unusual use-cases are possible: off-chain colored-coins, public key infrastructure with key rotation, a decentralized replacement for the DNS. For now though, such use-cases are speculative, and exist only in the minds of fringe ordinal theorists.
For more details on ordinal theory, see the overview.
For more details on inscriptions, see inscriptions.
When you're ready to get your hands dirty, a good place to start is with inscriptions, a curious species of digital artifact enabled by ordinal theory.