Icons, in many ways, work similar to bullet points. Both can make information easier to find and scan, as long as they’re placed in the right spot. Just as a bullet point will draw attention from the rest of the text on a page, icons will draw attention from the rest of the text on an interface.
User research has shown that in Western cultures, users scan from left to right and from top to bottom. For this reason, icons are best utilized as a visual cue when users see them before seeing the button label. Having icons positioned left of the button label allows users to see the icon first. If you place icons to the right of your button label, the icon loses its value and becomes little more than decoration. Icons should describe labels, labels shouldn’t describe icons.