Glossary
HTLC
Hash Time Locked Contract: a script that pays funds to whoever reveals a secret hash before a timeout, used for atomic swaps and payment channels.
An HTLC locks funds with two release paths: "send to Bob if he reveals the preimage of H(x) before block N", and "refund to Alice after block N". Revealing x to claim one HTLC reveals it for any other HTLC keyed off the same hash.
That property is the basis of atomic swaps across chains and of the Lightning Network's multi-hop payments. HTLCs predate modern bridges and remain one of the most trust-minimized cross-chain primitives, even if they are slower and less flexible than newer designs.