A measure of financial performance calculated as operating cash flow minus capital expenditures. Free cash flow (FCF) represents the cash that a company is able to generate after laying out the money required to maintain or expand its asset base.

EBIT(1-Tax Rate) + Depreciation & Amortization - Change in Net Working Capital - Capital Expenditure.

It can also be calculated by taking operating cash flow and subtracting capital expenditures.

Free Cash Flow is the real insight into the company.
It is operating cash flow - Capex = Free Cash Flow
It is an important metric looked at by investors specially banks when lending money.