The cash flow in a business plan is the change in the cash balance.
For example, the cash flow for a month would be a positive $10,000 if the balance was $10,000 at the beginning of the month and $20,000 at the end of the month. It is important to distinguish cash flow, which is the change in the balance, from cash or cash balance, which is the resulting ending balance.
More formally, cash flow is an assessment and understanding of cash coming into and flowing out of the venture in specific periods of time. This can be based on projections or actual cash flow.
For more, check out our article on forecasting cash flow.