Amortisation is paying off a debt in regular instalments that each cover the interest due and part of the principal, so that the balance reaches zero at the end of the term. A repayment mortgage, a car loan and most personal loans work this way. An interest-only loan does not, because none of its payments touch what you borrowed.
The instalment comes from one formula: payment = P × r ÷ (1 − (1 + r)^−n), where P is the amount borrowed, r the rate per period and n the number of payments. For £10,000 at 6% over 60 months, r is 0.005 and the payment £193.33. Because interest is charged on the balance still owed, early payments are mostly interest and late ones mostly repayment: the first £193.33 includes £50.00 of interest, the last only 96p. The CFPB describes the same shape, with the balance falling slowly at first and quickly towards the end. Laid out row by row, the process becomes an amortisation schedule.
Term length is the main lever. Spreading the same £10,000 over seven years instead of five cuts the payment to £146.09 but raises the total interest from £1,599.68 to £2,271.13. A lower payment bought with a longer term is rarely cheaper overall, and the monthly figure alone hides that.
Accountants use the same word for something else: writing down the cost of an intangible asset, such as a patent or software licence, over its useful life. Nothing on this site uses that sense.
The loan calculator, the mortgage calculator and the car loan calculator all amortise the loan you describe a month at a time, rounding each month's interest to the cent, so the yearly totals they show are sums of real monthly rows rather than estimates. The rent vs buy calculator uses the same balance to work out how much of the home you own in each year.