When you earn money by performing work, that income is usually subject to social security and Medicare taxes. Usually, when you work for a company, you are their employee. As their employee, you only have to pay half of these taxes while your employer pays the other half.
If you received a 1099-MISC with the amount of the income in Box 7, Non-employee Compensation, you are considered an independent contractor rather than an employee. As such, a Schedule C is required to be filed to claim the income and calculate the correct Social Security and Medicare taxes on your income.