LIGO is a programming language that aims to provide developers with an uncomplicated and safe way to implement smart contracts. Since it is being implemented for the Tezos blockchain LIGO compiles to Michelson—the native smart contract language of Tezos.
Smart contracts are programs that run within a blockchain network.
LIGO was meant to be a language for developing Marigold on top of a hacky framework called Meta-Michelson. However, due to the attention received by the Tezos community, LIGO is now a standalone language being developed to support Tezos directly.