First, you must have "compensation" -- usually this is income from working, either W-2 wages or schedule C self-employment. There are a few other odds and ends that count as compensation, see publication 590-a, Table 1-1.
If you are married, you can use your spouse's compensation to qualify to make an IRA contribution, up to the total amount of compensation. For example, the IRA contribution limit is $7500 for persons over age 50. If your spouse had $10,000 of compensation and contributed $6000 to an IRA, you could contribute a maximum of $4000.
If you are eligible, and if you make a contribution to a traditional (pre-tax) IRA, the contribution reduces your taxable income. How much that will actually save you depends on your overall income, deductions, and other tax situations.
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