Generally, icons represent a concept,an action or an idea.Icons are actually a graphic representation of an operation and convey it to the users. We see icons in applications and they are vital elements in UI/UX interface. Often, icons are used to depict an action in responsive website design. In that case, icons are useful for navigating through websites.
The user interface (UI) is the point of human-computer interaction and communication in a device. This can include display screens, keyboards, a mouse and the appearance of a desktop. It is also the way through which a user interacts with an application or a website.