Per IRS Instructions for Form W-2, page 9:
Instructions for Employee
Box 14. Railroad employers use this box to report railroad retirement (RRTA) compensation, Tier 1 tax, Tier 2 tax, Medicare tax, and Additional Medicare Tax. Include tips reported by the employee to the employer in railroad retirement (RRTA) compensation.
To report Box 14 income from the W-2 you received, go to our Form W-2 - Entering in Program FAQ.
If you received either of these forms, go to our Forms RRB-1099 and RRB-1099-R - Railroad Retirement FAQ for information and reporting steps.
Note that any link in the information above is updated each year automatically and will take you to the most recent version of the webpage or document at the time it is accessed.