Cash flow
The money actually coming into and going out of the business, and when — as opposed to profit on paper.
Profit is what you earned; cash flow is when the money moves. A sale made today but paid in two months is profit now and cash later. Most small businesses that fail are short of cash, not of profit.
A simple three-month look-ahead of money in and money out shows a gap while there is still time to close it.
Learn it in a lesson
See also: Working capital