Plain-English definition
An L2 processes transactions off the main chain, then posts compressed proof back to it for security. You get the base chain's safety at a fraction of the cost.
L2s now carry substantial reported TVL and activity. Reading which ones are deepening, and which depend on a single operator, is reading the next layer of the map. Reported USD TVL still needs price adjustment before it can be called deposit flow.
Why it matters
Layer 2 (L2) matters because crypto markets can look precise while still being shallow, crowded, or poorly sourced. A useful read is not just the number. It is the number, the size behind it, the context around it, and the part it cannot explain.
Simple example
A simple Layer 2 (L2) example is a reader comparing two venues with the same headline price but different depth. The deeper venue can absorb more capital before the trade, peg, or yield reading starts to move against the user.
How Bathymark uses this term
Bathymark uses Layer 2 (L2) to translate open market data into live liquidity readings. When the term touches a live page, the reading links back to the relevant chain, protocol, stablecoin, DEX, perps, or Signal so the source remains checkable.
Common mistake
The common mistake is treating Layer 2 (L2) as a complete signal by itself. Bathymark treats it as one instrument: useful when read beside liquidity, source, size, and what the number cannot prove.