What is the purpose of a layer?

Could you elaborate on the purpose of a layer in the context of cryptocurrency and blockchain technology? Are you referring to layers in terms of scalability solutions, such as Layer 2 solutions that aim to alleviate congestion on the main blockchain by offloading transactions to a secondary layer? Or are you perhaps referring to the multi-layered architecture of certain blockchain protocols, where different layers serve specific functions to enhance the overall performance and security of the network? Clarifying the specific context would help me provide a more accurate answer.