Items in comprehensive-income never touch the income statement, so they accumulate in their own equity line. A company with large foreign operations can carry a substantial negative AOCI purely because exchange rates moved, with no effect on reported profit.
It is worth checking before comparing shareholders-equity across companies, because a big negative AOCI depresses book value and inflates return-on-equity without any operating improvement.
Example: Northwind Tools carries negative $12M of AOCI, made up of negative $19M of translation losses on its European subsidiary and $7M of unrealised gains on interest rate hedges.
Related: comprehensive-income, shareholders-equity, return-on-equity, constant-currency