"Budgeting money" means that you actively make decisions on what you will spend money on and how much you will spend. For this you must actually know what your net income (spending money) is.
Net income = Gross income - Withholdings
Gross income is the amount of earnings you make before "withholdings".
Withholdings are monies that are taken out of your earnings.
Commonly withheld monies include income tax and FICA (social security payments). Withholdings may also include monies paid into other retirement accounts. On average, 28% of your gross income is withheld.
Many people do not have these amounts withheld monthly and pay these monies themselves after they receive their gross earnings.