Your tax return is the form you send to the government that shows your income and calculates your tax. The money the government sends back to you is your refund.
The tax return that you file in 2021 is your 2020 tax return, reporting the income that you earned in 2020. The refund that you receive in 2021, based on your 2020 tax return, is your 2020 tax refund.
You are correct in thinking that having paid less interest, or no interest, on your student loan in 2020 will reduce your 2020 tax refund. Without being able to see your tax return, we can't tell how much of a difference it will make. It could be a little complicated to figure out because eliminating the student loan interest deduction could affect other things.
You can get a rough idea by looking at your 2019 tax return. The student loan interest deduction is on Schedule 1 line 20. If you lose that deduction entirely, it will increase your taxable income by that amount. The effect on your refund depends on what tax bracket you are in. For example, if you are in the 22% tax bracket, losing the entire student loan interest deduction will reduce your refund by 22% of the deduction amount. It also increases your Adjusted Gross Income (AGI), so it could affect other deductions or credits that depend on AGI.
