The computer subsystem and the display subsystem are different, largely independent things. Regardless of what your computer is doing, the system that transports data between the video chip and the LCD will always be sending that data at 60 frames per second. It doesn’t care what your CPU is doing, it’s a bunch of separate independent pieces of hardware. Meanwhile, the rest of your computer is doing the game logic and rendering the frames and sending them to the video memory and that could be happening at any frame rate. Your screen will always be running at 60 hertz, but you could have anything from one frame per second to 3000 frames per second and that just refers to the number of times per second you are updating the frame buffer with new data.

Some video games have a setting called vsync, and what that does is it will limit updating the frame buffer to do so only once while the screen is showing one frame. The benefit of doing this is if you are updating your frame buffer in the middle of drawing a frame, you can have it where half the frame is the previous frame and half of the frame is the next frame, this is called tearing because it looks like the screen is being torn in half.