Employers can put just about anything in box 14; it's a catch-all for items that don't have their own dedicated box on the W-2. E.g., union dues, educational assistance payments, charitable giving you authorized, etc.
In TurboTax, enter the description from your W-2's box 14 on the first field in the row. Enter the dollar amount and select the correct tax category that goes with that description.
If none of the categories apply, scroll to the bottom of the list and choose Other–not on above list. Don’t worry. We'll figure out if it impacts your return or not. If we need more information, we'll ask you.
If box 14 is blank, just skip over it. Don't enter a 0 for any blank boxes.
Since there’s no standard list of W2 codes for Box 14, employers can list any description they choose. If the code is unclear, contact your employer and ask what the code represents.
Yes it goes on your tax return. 125 means a section 125 cafeteria plan and the Amount.
What is a 125 plan?
http://turbotax.intuit.com/tax-tools/tax-tips/Taxes-101/What-Is--Cafe-125--on-a-W-2-Tax-Form-/INF19508.html