#Liquidity101 " isn't a single, universally defined rule in finance. Instead, "Liquidity" seems to be used as a general hashtag or title for content that aims to explain the basics of liquidity, particularly in the context of financial markets, including traditional and cryptocurrency markets.

From the search results, it's clear that "Liquidity 101" often refers to:

* Understanding Liquidity: What it is (ease of buying/selling an asset without significant price change), why it matters (better prices, efficient trades, confidence), and how it's measured (tight spreads, deep order books).

* Market Dynamics: How concepts like makers and takers, order depth, and slippage relate to liquidity.

* Regulatory Aspects: In the crypto space, "Liquidity 101" can also touch upon new regulations aimed at improving market security and stability, such as Japan's new law requiring crypto platforms to keep user assets in separate custodial accounts after hacks.

* Smart Money Concepts in Trading: Many YouTube videos tagged "#Liquidity101" delve into how liquidity is understood and traded by "smart money" participants in forex or crypto markets, often involving concepts like "liquidity grabs," "break of structure," and "fair value gaps." These are more about trading strategies than a formal "rule."

In summary, the "#Liquidity101 rule" isn't a specific rule, but rather a catch-all term for foundational knowledge about liquidity in financial markets. It highlights the importance of liquidity for market efficiency, price stability, and regulatory compliance, and is often used in educational content for traders and investors.