It is a figure of speech that expresses clear comparison. It is used to make descriptions more emphatic or vivid. It uses the word as or like in comparing.

The figure of speech you are describing is known as a simile. Similes are often used in literature and everyday language to create vivid imagery and enhance descriptions by comparing one thing to another, using the words "as" or "like." For instance, saying "her smile was like sunshine" invokes a bright, pleasant image, making the description more engaging and relatable to the reader. Similes can be a powerful tool in writing, allowing authors to draw connections between different elements and to convey emotions or qualities in a more impactful way. They provide readers with a clearer understanding of what is being described, often evoking sensory experiences or emotions.