What it means is that you are a self-employed independent contractor with your own business. You will file a Schedule C to report the income and expenses next year. Also, be sure to send in estimated tax payments for your net profit.
For federal taxes, there are two amounts that need to be added
together for your estimated tax payments. The self-employment tax
rate of 15.3% plus your ordinary income tax rate (which depends
on your taxable income and filing status). The following article has easy
to read tables for this amount http://taxfoundation.org/article/2017-tax-brackets
How you figure out your estimated amount is to take your gross
self-employment income minus expenses to get your "net" taxable
self-employment income. Then, multiply that by the 15.3% self-employment
tax rate.
Then, look up the rate on the charts for your annual total taxable
income (in the link above) and multiple that by
the percentage for your total income you expect for
the entire year. Add those to tax
amounts together.