CPU time: How long it took for the CPU to process the game's logic
GPU time: How long it took for the GPU to render a frame
While having both lower is better, CPU time < GPU time is a better situation to be in. CPU time dictates the maximum frame rate you can get because the GPU isn't going to get anything to render until the CPU is done. So if you get a result like CPU time is 33ms, GPU time is 10ms, and wonder why you're getting say 30FPS, it's because the CPU is the bottleneck.