Adobe RGB is a colour space, meaning it's a defined set of colours that a screen or printer can reproduce. It was created by Adobe in 1998 to give creative professionals access to more saturated greens and reds than the standard sRGB colour space offers.
Most consumer displays and the web use sRGB, which is smaller and simpler. Adobe RGB is about 50% larger in its colour gamut, particularly in the green range. This matters if you're editing photographs or graphic design work and want to see colours as accurately as possible before sending files to print or clients.
A practical example: you're retouching product photography for a fashion brand. The greens in the fabric might look duller in sRGB than they actually are. With an Adobe RGB monitor, you see those greens more vividly and can edit with greater confidence that the final print will match your screen.
What to look for when buying: Check if a display explicitly supports Adobe RGB, usually shown as a percentage of the Adobe RGB colour space (look for 95% or higher). Professional monitors for photo or video work often advertise this. Be aware that Adobe RGB only matters if your software and workflow support it; most casual web browsing and gaming don't benefit. You'll also need to calibrate your monitor with a colourimeter to get accurate results.
If you're a casual user buying a laptop or gaming monitor, sRGB coverage is standard and sufficient. Only consider Adobe RGB if you're doing paid creative work and already use colour-critical software.