That's something to avoid, because it's a scam.
https://blog.obiex.finance/what-are-flash-coin-scams/What are Flash Coins?
A flash coin is a cryptocurrency that is sent to your wallet but doesn't stay there for long. It can be any cryptocurrency, such as Bitcoin (BTC), Ethereum (ETH), Ripple (XRP), or Solana (SOL).
I don't know what it is but information points out that it's scam.
If a coin sent to my wallet, but doesn't stay here for long time, it's scam. It is a coin in my wallet, assumes it is a non custodial wallet, and it should not leave out my wallet if I don't send it out.
It's my non custodial wallet, my private key, and my coin with full control by myself, if it leaves out of my wallet without my action, it's scam.
Reading the topic title, I think it is Flash Bitcoin as another Bitcoin fork or another scam altcoin that tries to use Bitcoin in its name.