Simple definition
L1 cache is a small, very fast processor cache usually located within each CPU core.
Purpose and use
L1 is a cache level close to core execution resources and designed for fast access.
How does it work?
Depending on architecture, instructions and data may use separate caches at this level.
Example and verification
Assess memory access and cache misses using tools appropriate to the architecture and application.
Points to watch
L1 size alone cannot compare processors; latency, organization and workload also matter.
In short
L1 emphasizes proximity and speed, generally with limited capacity.