L1 cache
Level 1 cache also referred to as L1 cache is a memory cache built into the CPU chip or packaged within the same module as the chip. Sometimes known as the "primary cache," an L1 cache is the memory closest to the CPU.
L2 cache
The L2 cache also referred to as secondary cache is a memory cache that is external to the CPU chip, typically located on the motherboard. An L2 cache feeds the L1 cache.
L3 cache
If the L2 cache is also integrated on the CPU chip, then the external motherboard cache becomes the L3 cache. The L3 cache feeds the L2 cache, which feeds the L1 cache, which in turn feeds the CPU.
