Dark liquidityInvestors typically trade securities on ‘lit’...

Dark liquidity
Investors typically trade securities on ‘lit’ exchange markets, such as ASX and Chi-X. On
these markets, buy and sell orders are visible and accessible to the rest of the market, before
they are executed.
Dark liquidity refers to buy and sell orders that are not visible to the rest of the market,
although the trades are typically published immediately after they take place. Dark trades are
usually done away from exchange markets and are accessible only to a subset of the market
(e.g. often limited to a market participant and its clients). There are also dark trading venues
known as ‘dark pools’ or ‘crossing systems’. A dark pool is a system that enables trading
away from lit exchange markets. A crossing system is a dark pool which is operated by a
market participant (a participant of a licensed market, with permission to directly access the
market to trade on behalf of their clients and/or themselves).

https://download.asic.gov.au/media/1338878/info178-published-15-January-2014.pdf