Icons create a better user experience. They must be simple and not distracting. They make the page more attractive than text-only pages. They must be carefully selected as they convey the personality of the website.
Read the great article: The Importance of Icons in Your Website Design. The prevalent source of icons is FontAwesome. They offer a React Integration.
Icons represent:
Brands and Logos
Search, Settings, User
Checkmarks, Numbers
Services, Topics, Sections
Icons improve the look of the website, making it more polished, professional and attractive.