A video card is a discrete dedicated circuit board, silicon chip and necessary cooling that provides 2D, 3D and sometimes even general purpose graphics processing (GPGPU) calculations for a computer. Alternate terms include graphics card, display adapter, video adapter, video board and almost any combination of the words in these terms.
Modern cards with integrated calculations for triangle setup, transformation and lighting features for 3D applications are typically called graphics processing units (GPU). Once rare, higher-end GPUs are now common and are sometimes integrated into CPUs themselves.
A video adapter is a discrete card in a computer, typically connected via PCI express in modern desktops. These cards have video RAM, and a GPU chip so that data can be sent to a computer's display. Today, almost all displays and video adapters provide digital connections such as HDMI, DVI or display ports but most also have digital-to-analog conversion for older Video Graphics Array (VGA) connections. VGA describes how data - essentially red, green, blue data streams - is passed between the computer and the display. It also describes the frame refresh rates in hertz and specifies the number and width of horizontal lines, which essentially amounts to specifying the resolution of the pixels that are created. VGA supports four different resolution settings and two related image refresh rates.
In addition to VGA, most displays today adhere to one or more standards set by the Video Electronics Standards Association (VESA). VESA defines how software can determine the capabilities of a display. It also identifies resolutions settings beyond those of VGA. These resolutions include 800 by 600, 1024 by 768, 1280 by 1024, and 1600 by 1200 pixels, although they have largely been replaced by wide screen formats.
Wide screen (16:9 aspect ratio) adoption became widespread in response to marketing. Manufacturers were motivated by cheaper display production due to standards that matched those of HDTV -- 1280x720 (720p) and 1920x1080 (1080p). The market acceptance of wide screeens was also boosted because they enhance the display of movies and games.
The simplicity of porting console video games to PC with these standard resolutions also helped bring about mainstream adoption. Today it is not uncommon for video cards to support ultra-wide displays of 21:9 in resolutions of 2560x1080 or 3440x1440. 4K and even 8K resolutions can be run by capable cards and even multiple monitors for up to six screens. Many graphics cards support multiple-card setups to drive these demanding configurations.