What is the difference between L1 and L0?

Could you please elaborate on the distinction between L1 and L0 in the context of cryptocurrency and finance? Are they referring to specific layers of blockchain technology or perhaps a categorization of certain tokens or assets? If they are layers, how do they differ in terms of functionality, security, and scalability? Additionally, are there any notable examples of projects or platforms that utilize L1 and L0, and how do they utilize these layers to their advantage?