A saved search is built from criteria (which records to include) and results (which fields to show), and NetSuite lets you reuse that combination as a list, a report, a dashboard portlet, or a scheduled email that lands in someone's inbox on a recurring basis. Built right, it replaces a lot of what used to be a manual filter-and-export routine.
They can trigger action too. A saved search set up as an alert can notify someone the moment a record matches its criteria, a customer's balance crosses a threshold, a case sits open past a certain number of days, without anyone running the search by hand to check.
For straightforward reporting, counting open orders by region, listing overdue invoices, pulling a customer list by segment, a saved search usually covers it with no custom development at all.