Liquidity (exchangeability) is the ability of tokens to buy and sell without significant changes in the price of assets.
The liquidity of assets is determined by how easy it is to convert them into fiat. A token is liquid when the number of offers to sell at the market price matches the demand.
If there are significantly more offers to sell than offers to buy, then the token is either illiquid or low liquidity. In this case, the seller is forced to lower the price or abandon the idea of selling his assets.