In addition to conveying brand personality through color and style, icons must first and foremost communicate meaning in a graphical user interface. Icons are, by definition, a visual representation of an object, action, or idea. If that object, action, or idea is not immediately clear to users, the icon is reduced to mere eye candy — confusing, frustrating, eye candy — and to visual noise that hinders people from completing a task.

A user’s understanding of an icon is based on previous experience. Due to the absence of a standard usage for most icons, text labels are necessary to communicate the meaning and reduce ambiguity.

https://www.nngroup.com/articles/icon-usability/