Overlays & Surfaces
Dialog
also known as dialog box
A dialog is a container that opens a short 'conversation' between the app and the user, requesting input, confirmation, or a choice. It's the component itself, and it can be either modal (blocks the rest of the page) or non-modal (leaves the page usable). Dialogs typically have a title, body content, and action buttons.
See it live — shadcn/ui · MUI · Ant Design
Don't confuse it with
A dialog is the component (a window that converses with you). 'Modal' describes a behavior (blocking the background). So a dialog can be modal or non-modal; not every dialog is modal, and not every modal is a dialog.
In the wild
The 'Save changes?' window in Google Docs when you close an unsaved file is a dialog.