The ability of a business to turn its assets into cash to pay it's current liabilities
Business owner and investors can use liquidity as a measure of how healthy the business is, it doesn't have too may debts and it can easily pay its bills
Ways to measure liquidity
Current ratio
Acid test ratio
Current assets are assets that can be converted into cash relatively easily. E.g: cash, inventory
Non current assets are long term or fixed assets that are used within a business and contribute to it's actual operations E.g: land, plantproperty and equipment (PP&E)
Acid test ratio - is a harsher test of liquidity because you can not guarantee to sell all of the stock. Stock can also spoil become obsolete or just go out of fashion.
Acid test ratio of less than 1:1 means the current assets do not cover its current liabilities.
However some retailers with strong cash flow and fast moving stocks may have an acid test of 0.4:1 and be fine, it depends on the industry.