What are symbols or icons?
“Icon” and “symbol” are terms that we often use interchangeably, but there's actually a subtle difference: An icon is a literal, visual representation of the thing it represents, whereas a symbol can be a more abstract representation of something.
Why should icons be used?
Benefits of Icons
Icons make good targets. They are typically sized large enough to be easily touched in a finger-friendly UI. They save screen estate. Icons can be compact enough to allow display more content on a relatively small space.