Liquidity is the usable balance distribution across your channels. Capital sitting on the wrong side of a channel cannot forward or receive as needed.
Why this matters
A node with lots of bitcoin locked but zero inbound capacity still cannot get paid. Liquidity ops is the business of Lightning routing and merchant receive capacity.
Analogy
A highway with all cars stuck on one side of a toll bridge. You need flows (or trucks repositioning cars) to free lanes in both directions.
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Worked mental model
Re-read the diagrams in this lesson once out loud in plain language. If you cannot explain the flow to a friend without jargon, pause and revisit Mastering Bitcoin / Mastering Lightning chapters linked in Resources. Chapter references are intentional, not decorative.
Hands-on habit
Every protocol idea should be paired with one local experiment:
- Reproduce the happy path on regtest (or Polar for Lightning)
- Break it on purpose (wrong fee, expired invoice, offline peer)
- Write down what error you saw and which layer produced it (wallet, node, mempool, peer)
That habit turns reading into builder instinct.
Glossary check
Pick three terms from this lesson and define them in one sentence each without opening notes. Weak definitions mean the lesson is not finished yet.
Resource order
Use Resources in order: narrative book chapter first, then BIP/BOLT for precision, then implementation docs for commands. Jumping straight to RPC flags without the mental model creates brittle knowledge.
Next steps
Multipath payments, splitting payments when one path cannot carry the full amount.