Monetary supply (physical) circulating in the economy versus money in a bank account (available for bank to loan out as well as for me to withdraw); interest bearing
Fractional reserve banking (ability to stretch / expand) as you don't need to supply money for all of whats on the books at one time.
Wealth tied up in e.g. a house - represents wealth, can raise funds against that
Look up definitions for these
Liquidity
haircuts etc.
See e.g. Archegos Capital Management liquidity crisis
Relevance here is the money supply question - reduction in asset price → margin call
Who has custody of the stock v who has title; price impact
In general - issues that may have some impact on the money supply