Net operating losses can be used to reduce future tax payments. For example, let's assume Company XYZ has taxable income of $1,000,000 and tax deductions of $1,300,000. Its net operating loss is $1,000,000 - $1,300,000 = - $300,000.
Company XYZ will probably not have to pay taxes that year (because it didn't have any taxable income). But let's assume that next year, Company XYZ makes a lot more money and records $500,000 of taxable income.
If Company XYZ is taxed at a corporate tax rate of 40%, it would need to pay $500,000 x 40% = $200,000 in taxes. But because it incurred an NOL last year, it can apply that NOL to this year's tax bill, reducing it significantly (or even to $0, depending on the jurisdiction Company XYZ is in). Company XYZ could also carry the NOL "back" and apply it against taxable income in preceding years.