Let's look at different types of icons and how they impact the user experience:
Confusing and conflicting icons
When you use commonly-used icons with opposing meanings, you'll run into trouble. For example, the heart and the star are two icons that are commonly misunderstood by users. Assume you're using an app that has no text labels for the following icons. What exactly do these words imply? If you tap one of them, what happens? For many users, these icons are difficult to decipher precisely. The meaning of this icon can only be deduced by interacting with it.
Like a star and the heart, there are certain icons we're used to seeing in numerous situations, although they serve slightly different tasks in each product. That's not even taking into account the differences in conventions between iOS and Android. Users may be confused by the fact that standard bar icons differ significantly from one OS to the next.
Outdated icons
Many regularly used icons refer to old or obsolete technologies. Many of us who remember using floppy disk drives have no problem with the Save icon still appearing in many apps, but many users born after 1995 perceive it as a peculiar oddity that elderly people insist on holding to. Continuing to utilize icons like the floppy disc might make your business appear outdated to a younger audience.
Unique icons
When your product has unique functionalities beyond the conventional activities of sharing, favoriting, uploading photos, writing text, and so on, one of the most difficult icon issues is deciding what to do with it. What should you do if your product offers unique features that go beyond the normal sharing, printing, and so on? With a single picture, how can you communicate complicated ideas like analyzing your purchase history or tracking?
Designers frequently hide functionality behind icons that are difficult to recognize. Of course, designers believe that consumers will figure out what the icons imply. However, this does not always occur. When Google opted to conceal other programs in Gmail behind an uncertain icon, they received a flood of support queries, such as "Where is my Google Calendar?"
Many designers attempt it, and many designers fail. It may be an entirely different experience for first-time users, regardless of how much sense an icon seems once you understand what it's meant to signify.
Universal icons
By definition, an icon is a graphic depiction of an item, action, or concept. There are several icons that are almost universally recognized by users. Such examples are the home, print, and shopping cart icons. There is only one issue with this group: "universal" icons are hard to come by. Apart from the examples given above, many icons remain confusing to users owing to their many associations.
Easy icons
There are a few icons that are almost universal in their appeal. A house-shaped icon will almost certainly lead you to the homepage or home screen, while a shopping cart will allow you to make a purchase. Most of the time, icons aren't the best location to be creative. Your brand message may be communicated through your other design aspects. The initial duty of your icons is to direct your users to where they need to go. For basic functions, fancy or too smart icons might detract from the user experience.