Smooth Scroll is a script written by our development team to make the scrolling experience much better and more performant. Meanwhile the script is used to have a smooth and performant Parallax effect. That is why the Smooth Scroll option is enabled by default. If you disable this option the Parallax and, in some cases, Fixed Background effect will not work. Also, if the smooth scroll is disabled, the anchor scrolling will not work. To access the Smooth Scroll option you can go to Theme Options > Global Settings > Site Settings > Smooth Scroll.