Non-wage income is any income you get that is not from a job and not reported on a W-2 (or a Schedule C, if Self-employed). This definition applies to the IRS, NJ and any other state that has an income tax.
Non-wage income is not subject to employment taxes (Social Security and Medicare).
Examples of non-wage income would be disability income, retirement plan/pension income, social security, unemployment, paid family leave, child support, alimony, investment income, and interest from a bank account.