In the early days of the graphical user interface (GUI) up to today, icons serve the purpose of communicating the function of a particular application or feature. Many icons that were designed at the birth of the GUI were designed to be literal representations of the real world analog. You store documents in folders in real life, so when you see folders represented on screen you can easily intuit their purpose. You throw documents you don’t need into a trash can (or a recycling bin if you’re eco-conscious), so that’s how the delete function is presented to you.
We still see this same idea applied to icons designed in the modern era, even though computers are much more familiar now. Instagram is a popular modern example, its icon is representative of an instant camera like those from Polaroid. The icon is a brilliant representation of the apps function, as it’s basically the digital equivalent of the Polaroid camera, giving you the ability to instantly share any photo you take.
However, there is some concern with this approach as more and more kids are being born into our digital world with very little experience with many of the things that are represented in our icons. On the iPhone for example, the icon for the phone app is a symbol of a landline phone receiver which I would wager many children born in the last 10 years will have had very limited, if any, exposure to. Many of these types of icons are so engrained in the minds of today’s adults though that changing them up can be a difficult process.
Consider Your Design Choices
The truth is, making an icon that resembled a real-world object can be a good design approach, but as a designer you have to consider wether the metaphor works with your audience. Representing a music app with a vinyl record, a cassette tape, or even a CD isn’t going to make sense with a younger audience who probably have limited to no experience with those mediums. However, something like a pair of headphones will make sense to almost everybody.
However, sometimes there are icons rooted in years of tradition. The universally used icon for the save function, the floppy disk, doesn’t only not make sense in today’s world, but probably makes even less sense to people born since the turn of the century. But there is no viable alternative, and most software designers end up omitting an icon for that specific function. But there are standard icons out there that could serve to be updated.