In the world of blockchains, Layer 1 refers to the actual blockchain itself, while the term layer 2 includes projects built on top of the mainnet L1 blockchain. Layer 2 solutions are commonly built and used to offload transactional burden from the main Layer 1 blockchain and ultimately serve as a scaling solution. One notable example of a Layer 2 technology on the Bitcoin blockchain is the Lightning network.
NFT Term
Layer 2
Definition of Layer 2 from the NFTguild.com glossary.

