It is because for the most part we are used to sub 60FPS videos. Most movies and TV shows are done at 24FPS. Have you ever wondered why they look so different to a video you take with a camera? That is one of the reasons.
That is what the 60 means. It is 720p/1080p running at 60 frames per second.
60FPS is smoother, there are more frames being shown per second and it seems faster but it is just smoother.
I don't mind it although it can sometimes be a bit jarring. I do hate it when it is applied to a movie that was filmed at say 24FPS as it makes the film look like a soap opera.