The sRGB color space was created to help ensure color consistency as an image moves from camera or scanner to monitor and printer; the idea was to create a spectrum of colors that all devices can reproduce. (You select the color space as you process and convert Raw images, not when you capture them.)
However, the sRGB color spectrum leaves out some colors that can be reproduced in print and onscreen, at least by some devices. So, as an alternative, your camera also enables you to shoot in the Adobe RGB color space, which includes a larger spectrum (or gamut) of colors. Some colors in the Adobe RGB spectrum can’t be reproduced in print. (The printer just substitutes the closest printable color.) Still, you can shoot in Adobe RGB to give yourself more options.
However, that doesn’t mean that it’s right for you. If you print and share your photos without making any adjustments in your photo editor, you’re better off sticking with sRGB because most printers and web browsers are designed around that color space.If you do want to switch to Adobe RGB, set the camera to an advanced shooting mode and make the adjustment via the Color Space option on Shooting Menu 2. In all other modes, you're locked into sRGB.
When seen on your computer, Adobe RGB images start with an underscore, as in _MG_0627.jpg. Pictures captured in the sRGB color space start with the letter I, as in IMG_0627.jpg.