That would indicate that your wages are exempt from social security and medicare tax. I can think of two reasons for this. You are a church pastor or a member of a religious order that has taken a vow of poverty, or you are a student and your employer is the school where you attend. There may be other reasons, but you will need to tell us what kind of job you have.
[Edited to add]
A third reason, you are under the age of 18 and you are employed by your parents.
Here are some other reasons.
https://turbotax.intuit.com/tax-tips/irs-tax-return/who-is-exempt-from-paying-social-security-tax/L3...
