Roth 401(k) Plan

An employer-sponsored Roth 401(k) plan is similar to a traditional plan with one major exception. Contributions by employees are not tax deferred but are made with after-tax dollars. Income earned on the account from interest, dividends, or capital gains, is tax-free.

Source: http://investor.gov/glossary/glossary_terms/roth-401k-plan#.Us7v7WRDuEg