Well students can, write off expenses, but any tax software you use will rightfully swap that for the standard deduction. I don't know what it is this year but it usually exceeds whatever tax deductions you can claim as a student.

Really savvy business owners or other entrepreneurs can report expenses in a way that exceeds the standard deduction and lowers their tax liability. Things like business expenses and the interest on mortgage loans are big chunks of what people claim for "itemized deductions". If the total of itemized deductions exceed the standard deduction, it lowers the amount of your income that can be taxed at all. The lower taxable income decreases your tax liability. The lower tax liability means you get a bigger refund if you've reported standard withholdings when your turn in your form W-4 to your employer.