Terra is a blockchain protocol that uses stablecoins backed by fiat currency to support price-stable global payment networks.
According to the white paper, Terra combines the price stability and widespread adoption of fiat currencies with the censorship-resistance of Bitcoin (BTC) and provides quick and low-cost transactions.
The LUNA token and UST are mutually dependent, as the success of the Terra ecosystem is dependent on the adoption of UST as a stablecoin.
LUNA invests in UST and is burned as UST demand rises. However, if UST is deemed unstable, the value of LUNA may fall.