GLONASS (Global Navigation Satellite System) is a space-based satellite navigation system analogous to the GPS, operated by the Russian Aerospace Defense Forces. It works alongside GPS (Global Positioning System of USA) to provide location information to compatible GLONASS devices. With an additional 24 satellites to utilize, GLONASS compatible receivers can acquire satellites up to 20% faster than devices that rely on GPS alone.
The GLONASS system was initially created as an alternative to the GPS system operated by US Dept. of Defense. Fortunately, we greatly benefit from those two systems working simultaneously rather than just one of them. Basically, GLONASS is no different than GPS when it comes to features, global coverage and also precision.