Standard reports cover the predictable stuff: income statements, balance sheets, AR aging, inventory valuation. They're built-in, familiar to anyone who's used accounting software before, and most businesses never need to touch the report builder to get what they need out of them.
Dashboards are the home-screen view: KPI scorecards, trend graphs, and portlets a user can arrange to see the numbers that matter to their role the moment they log in. They're built from saved searches and reports underneath rather than a separate data source, which is why getting a dashboard right usually starts with getting the saved search or report behind it right.
SuiteAnalytics, built on what NetSuite calls workbooks, is the deeper layer. It supports pivot tables, charts, and joining data across record types in ways the standard report builder and saved search criteria builder don't reach, closer to a lightweight BI tool living inside NetSuite than a traditional financial report.