A 403(b) account is a qualified retirement savings account similar to a 401(k).
Typically, 403(b)s are set up by public schools, 501(c)(3) organizations, and cooperative hospital service organizations for their employees. Self-employed ministers can also contribute to a 403(b).
Your contribution is reported in Box 12 of your W-2 with the letter code E or BB.
Because your contribution is already accounted for on your W-2, do not re-enter it in the retirement section.