See this link: https://turbotax.intuit.com/tax-tools/tax-tips/Taxes-101/What-Is--Cafe-125--on-a-W-2-Tax-Form-/INF19...
This is showing that your employer had a "Cafeteria" benefit plan, which could have covered a number of things, such as adoption and dependent care assistance, health insurance, 401k and group term life insurance policies. The benefits are paid for pre-tax dollars, which means you aren't taxed on them at the federal level. Different states could tax you on this amount.
There's nothing special for you to do, just report your W-2 the way it's written. You don't have to enter the Cafe 125 amount on your return.