Libra is value backed in to tiers. The first is single-currency stablecoins in US dollars, British pounds, euros, and Singapore Dollars, referred to as Libra$, Libra €, etc. Beyond this is a global stablecoin (LBR) that is a basket of those single-currency stablecoins. So Libra is available through many individual currencies but LBR is the catch all of stablecoins, remaining backed by its own stablecoins which are backed by different currencies.