K2XX is just the generic name for the 2014/2015+ GM full size truck/SUV platform. The "XX" can be various different letters to denote which specific vehicle within the platform.
Sort of like "GMT-900" "GMT-800", etc. And then there are more specifics, like GMT-931 is an Avalanche, etc.
2014+ Chevrolet Silverado Crew Cab (K2CC)
2014+ GMC Sierra Crew Cab (K2CG)
2014+ Chevrolet Silverado Extended Cab (K2EC)
2014+ GMC Sierra Extended Cab (K2EG)
2014+ Chevrolet Silverado Regular Cab (K2RC)
2014+ GMC Sierra Regular Cab (K2RG)
2014+ Chevrolet Tahoe (K2UC)
2014+ GMC Yukon (K2UG)
2014+ Chevrolet Suburban (K2YC)
2014+ GMC Yukon XL (K2YG)
2014+ Cadillac Escalade (K2XL)