Terra (LUNA) is a public blockchain protocol that emerged from Terra Classic. Terra Classic is home to the algorithmic stablecoin TerraClassicUSD (UST). It's now-renamed LUNC token collateralized UST, which crashed in a bank run in May 2022. That devalued LUNA to virtually zero and caused a launch of a new chain — resulting in Terra Classic and Terra. Read a full breakdown of the Terra crash here.