An expense is something that money is spent on.
Examples: food, housing, travel, clothes, cars, insurance, debt payments, entertainment, etc.
Pro Tip: All your expenses should be revolving around your goals. Create a spending plan, or budget, to see what you are spending on and think about why you are spending money on each item. Is it a need? Is it helping you reach your goals? If not, consider cutting it out of your life or be honest and change your goals to include that expense.