The macOS feature that lets you view all open windows in a single screen is Mission Control. It shrinks and arranges open windows so you can quickly identify and select the one you need.
Mission Control debuted in Mac OS X Lion in 2011, combining and renaming parts of earlier features including Exposé, Dashboard, and Spaces. Exposé itself first appeared in Mac OS X Panther in 2003 and was focused mainly on exposing windows; Mission Control expanded the idea to include virtual desktops, called Spaces, as well.
A common mix-up is answering Exposé, because Exposé was the original name for the all-windows view. On current Macs, Mission Control can be opened with the F3 key on many Apple keyboards, by swiping upward with three or four fingers on a trackpad, or through a configured hot corner. The exact gesture and shortcut can vary by keyboard and system settings.