The phrase "extra payments" means paying more than the required amount towards something, like a loan or bill. It helps to pay off the debt faster or reduce the overall cost. Full definition
You can do this by not using your credit cards and by making extra payments on existing debts. (mybanktracker.com)
If the payments are too high, you can always achieve similar results, although at a higher interest rate, by making extra payments on your principal when you have funds available. (shoprate.com)
By taking out a 15 year loan, you are basically committing to making extra payments for 15 years in return for usually around an 0.5 % decrease in the interest. (biggerpockets.com)