Screenshot

A screenshot, screen capture, screen cap, cap, screen dump, or screengrab is an image taken by a person to record the visible items displayed on the monitor, television, or other visual output device in use. Usually, this is a digital image using the operating system or software running on the computer, but it can also be a capture made by a camera or a device intercepting the video output of the display.

In the 1980s, computer operating systems did not universally have built-in functionality for capturing screenshots. Sometimes text-only screens could be dumped to a text file, but the result would only capture the content of the screen, not the appearance, nor were graphics screens preservable this way. Some systems had a BSAVE command that could be used to capture the area of memory where screen data was stored, but this required access to a BASIC prompt. Systems with composite video output could be connected to a VCR, and entire screencasts preserved this way. Screenshot kits were available for standard (film) cameras that included a long antireflective hood to attach between the screen and camera lens, as well as a closeup lens for the camera. Polaroid film was popular for capturing screenshots, because of the instant results and close-focusing capability of Polaroid cameras. In 1988, Polaroid introduced Spectra film with a 9.2 x 7.3 image size more suited to the 4x3 aspect ratio of CRT screens.

Screenshots can be used to demonstrate a program, a particular problem a user might be having, or generally when display output needs to be shown to others or archived. For example, after being emailed a screenshot, a Web page author might be surprised to see how their page looks on a different Web browser and can take corrective action. Likewise with differing email software programs, (particularly such as in a cell phone, tablet, etc.,) a sender might have no idea how their email looks to others until they see a screenshot from another computer and then can adjust their settings appropriately.

https://en.wikipedia.org/wiki/Screenshot