In short, your taxable income is your gross income minus available deductions. Here’s a simplistic breakdown:
Determine your filing status. This will inform which deductions you’re able to take because spouses filing separately can’t both claim the same deduction.
Gather up and add together all your income sources. This includes your salary, plus any tips and side income you earned over the year.
Calculate your deductions. For most, this means taking the standard deduction ( $12,950 for singles and  $25,950 for married couples filing jointly or qualifying widower).