Application scenarios of LBR coin?

Hi, LBR coin is synthetic, Coin1 and Coin2 are non-synthetic. LBR must be backed by the reserve of fiat coins in order to exist. but still don’t quite understand the significance of LBR.

I’m not sure if your question is about LBR in Move or LBR more generally. If the second one, here is what the Libra whitepaper says:

For countries that do not have a single-currency stablecoin on the Libra network, we believe ≋LBR is a neutral and low-volatility alternative that could ensure users in such regions can benefit from accessing the network and increased financial inclusion. In this context, ≋LBR could operate as a settlement coin in cross-border transactions, and people and businesses could convert the ≋LBR they receive into local currency to spend on goods and services through third-party financial service providers. For example, consider a Libra user in the US wanting to send money to their family in another country. The sender in the US would likely use ≋USD as their default Libra Coin to make the transfer. If the receiver lives in a region with a different single-currency stablecoin on the Libra network, the sender could transfer that single-currency stablecoin or the receiver could convert ≋USD to that single-currency stablecoin or local currency through a third-party financial service provider, providing a convenient and simple option for the receiver to access and use the funds. If a single-currency stablecoin is not available, the transfer could be made in ≋LBR. The receiver could convert ≋LBR into their local currency through a third-party financial service provider to buy goods and services in that currency.

Thank you for your answer, it answers my question. I have seen the create and unpack of LBR , does it provide an interface for the exchange of a certain one stablecoin to LBR? If provided, how often to_lbr_exchange_rate needs to be updated.

There is no on-chain interface for exchanging single-currency stablecoins for LBR. The to_lbr_exchange rate is only used for normalizing the value of currencies (which is needed in a few cases such as prioritizing transactions based on gas price).