Timing Analyzer caters for all PVT effects (Process, Voltage and Temperature). In the highlighter corners, the voltage and temperature are the same, but it covers the process variance. Hope that helps.
Semiconductor chips are subject to variation during fabrication (https://en.wikipedia.org/wiki/Process_variation_(semiconductor)). That means when you purchase multiple units of the same device, some will be slow and some will be fast. To make sure all of them work normally functionally, users will need to ensure timing requirement is met in all timing corners.
