Layer 2 of Bitcoin (BTC): An ecosystem mapping
The Bitcoin network can transact in fractional values, e.g., from millibitcoin (1/1000th of a bitcoin) down to 1/100,000,000th of a bitcoin, which is known as a satoshi.
David A. Harding • Mastering Bitcoin
The future use of Bitcoin for small payments will likely not be carried out over the distributed ledger, as explained in the discussion on scaling in Chapter 10, but through second layers. Bitcoin can be seen as the new emerging reserve currency for online transactions, where the online equivalent of banks will issue Bitcoin‐backed tokens to users
... See moreSaifedean Ammous • The Bitcoin Standard: The Decentralized Alternative to Central Banking
To address this, the community chose a rollup-centric approach. The idea is simple: Instead of hosting all applications on Ethereum, the focus is on rollups that offer faster, cheaper transactions while still settling back on Ethereum. As a result, you get faster, cheaper transactions, but still keep Ethereum’s security.