Your browser does not support playing HTML5 video. The higher frame rate is applied to camera movements, like how the steam and mobile clients work, which results in a smoother feel when moving the camera with mouse or keyboard input.
For most users, this will be 60 FPS, unless you have a display and GPU which supports a higher refresh rate. The GPU plugin has a new Unlock FPS option which disables the 50 FPS hard cap on the client and allows the client to render frames at the maximum rate supported by your system.
