It depends.
If you are claimed as a dependent on your parent's tax return -
- you don't have to file if your W-2 income is $6300 or less. You may want to file just to get your withholdings back.
- you must file if your self-employment income (not W-2- but cash, check, 1099-misc) is more than $400
If you are not claimed as a dependent:
- you do have to file if self-employed income is more than $400
- if it's W2 income - no need to file unless to get your withholding back