As layer 1 blockchains, Bitcoin and Ethereum, have always been plagued by the 'Blockchain Trilemma'. This means that, one of three features (scalability, decentralisation & security) needs to be sacrificed for the blockchain to function For instance, on the Bitcoin and Ethereum Blockchains, scalability is traded for security and decentralisation. So, while data is stored in a secured distributed ledger, these blockchains suffer in terms of transaction speeds, especially as the number of users on the network increases.

Bitcoin has a transaction per second (TPS) speed of 7, whereas Ethereum has a TPS of 15. These are extremely slow compared to other payment services like Visa, which has a TPS of 45,000. Developers have turned to layer 2 solutions to address this gulf in processing speeds

source:

https://www.cnbctv18.com/cryptocurrency/what-is-a-layer-2-blockchain-13267932.htm