Roth IRA contributions are not deductible, but contributions to traditional IRA's are deductible.  

Because you do not get a tax deduction for contributions to a Roth IRA, the money in the IRA grows "tax-free" and therefore distributions, when they begin, are also ''tax-free''.

If you have the flexibility to make either a traditional or Roth IRA contribution, then you need to weigh carefully the advantages of one versus the other.  Here is more info on the difference between these two account types:  https://ttlc.intuit.com/replies/3300134