# Definitions

## Foundational Definitions

**Submarine Swap** - an atomic on-chain to off-chain swaps of cryptocurrencies. REDSHIFT currently supports swaps of on-chain assets like Bitcoin, Ether, or DAI for Lightning Bitcoin. Also referred to as just "swap".

**HTLC** (Hash Time Lock Contract) - A type of transaction that puts on-chain funds in escrow until someone unlocks them with a preimage or the timelock expires.

**Preimage** - A string of characters returned when successfully paying a Lightning Network invoice. Think of it as a password. It is used to unlock on-chain funds that are locked up in an HTLC.

**Liquidity Provider** - The counter-party to a swap that will pay the Lightning Invoice in exchange for an on-chain asset like Bitcoin, Ether, or DAI.

**Quote** - The price a liquidity provider returns when asked to pay an invoice. Denominated in the requested asset.