SXGA is an acronym for Super eXtended Graphics Array referring to a standard monitor resolution of 1280×1024 pixels. This display resolution is the "next step" above the XGA resolution that IBM developed in 1990.
The 1280×1024 resolution is not the standard 4:3 aspect ratio, but 5:4 (1.25:1 instead of 1.333:1). A standard 4:3 monitor using this resolution will have rectangular rather than square pixels, meaning that unless the software compensates for this the picture will be distorted, causing circles to appear elliptical. There is a less common 1280×960 resolution sometimes unofficially called "SXGA-" (to avoid confusion with the "standard" SXGA) that preserves the common 4:3 aspect ratio.
SXGA is the most common native resolution of non-widescreen 17" and 19" LCD monitors. An LCD monitor with SXGA native resolution will typically have a physical 5:4 aspect ratio, preserving a 1:1 pixel aspect ratio.
Apple Computer referred to displays with this resolution as "two-page displays", because they could be used to display two A4 pages side-by-side at a resolution of 72 dots per inch. Sony manufactured a 17" CRT monitor with a 5:4 aspect ratio designed for this resolution. It was sold under the Apple brand name.
SXGA is also a popular resolution for cell phone cameras, such as the Motorola Razr and most Samsung and LG phones. Although being taken over by newer UXGA (2.0 megapixel) cameras, the 1.3 megapixel is the most common for the time being.
Any CRT that can run 1280x1024 can also run 1280×960, which has the standard 4:3 ratio. Displaying any 4:3 resolution on a 5:4 monitor, like a TFT with a native resolution of 1280×1024, will look stretched. But on a TFT, displaying any other resolution than the native one is not a good idea anyway, as the image needs to be interpolated to fit in the fixed grid display.
There is much speculation on the origin of SXGA. Some believe its use began back in the mid-1980s, as an upgrade from XGA (1024×768). At the time, memory was extremely expensive. Using 1280×1024 at 8-bit color depth allowed 1.25 MB of video RAM usage, fitting nicely with available RAM chip sizes.