Stands for "Standard RGB" (and RGB stands for Red-Green-Blue"). All the colors you see on your computer display are made up various mixtures of red, green, and blue light. While this works great for individual displays, the same colors are often displayed differently on different screens. For example, dark red on one screen may look like red-orange on another. When you add printers, scanners, and digital cameras to the mix, the problem is magnified even more.
To help achieve a greater color consistency between hardware devices, the sRGB standard was created in 1999. It defines a gamut of colors that represents each color well and can be used by CRT monitors, LCD screens, scanners, printers, and digital cameras. It also has been incorporated into many Web browsers to make sure the colors on Web pages match the color scheme of the operating system. Because of the color consistency sRGB creates, most hardware devices that work with images now use it as the default setting.