No, "NVIDIA G-SYNC Ready" and "NVIDIA G-SYNC Compatible" are not the same thing, although they offer similar features.
"NVIDIA G-SYNC Ready" refers to monitors that have been tested and certified by NVIDIA itself as compatible with NVIDIA's G-SYNC technology. These monitors have met specific hardware requirements and have been recommended by NVIDIA as the optimal choice for use with NVIDIA graphics cards.
"NVIDIA G-SYNC Compatible," on the other hand, refers to monitors that have not been directly tested by NVIDIA but still support G-SYNC functionality. NVIDIA has established a certification program where certain adaptive sync monitors from other manufacturers can be certified as "NVIDIA G-SYNC Compatible." These monitors have shown that they can successfully use NVIDIA's G-SYNC technology and offer good compatibility.
Essentially, this means that "NVIDIA G-SYNC Ready" monitors that have been tested and certified by NVIDIA itself to provide the best possible performance, while "NVIDIA G-SYNC Compatible" monitors provide similar functionality but come from other manufacturers and may not meet all of NVIDIA's specific requirements.
If a monitor is described as G-Sync Compatible, that monitor lacks necessary hardware and testing performed by NVIDIA. These displays do not have NVIDIA processors, but have at least been validated by NVIDIA and offer variable refresh rates without tearing or judder. Monitors that do not have a "Compatible" suffix or do have the "Ready" name suffixoffer an experience without tearing, judder, or input lag thanks to an NVIDIA G-SYNC processor. Gaming enthusiasts and pro gamers can look forward to the variable refresh rate (VRR) over the entire frequency range and variable overdrive, which are supposed to provide a crisp picture and first-class gameplay.