If a website is Perceivable it is easy for the user to identify interactions on the website. Users need to be able to review an interface and identify interactions. As not everybody interacts in the same way, it is important to provide hints and indicators such as buttons, icons, textiles, textures etc. Allow for the user to see that something can be clicked on or tapped. In doing this the usability and accessibility and users perceive objects on the interface.

Reference: https://cristianweierick.wordpress.com/2013/10/30/5-essential-core-principles-of-interactive-design-2/