Answer:
Figurative language is used when words do not use their literal meaning, which means figurative language is usually recognizable but not explicit. I do not understand the "why" part of this question but above is a loose definition which hopefully answers your question.
Examples:
Metaphors directly compare two things without using 'like' or 'as' -
metaphor: she is a shining star.
Similes are comparisons that do use 'like' or 'as' -
simile: her eyes sparkled like diamonds.
Personification: describing an inanimate object with human-like characteristics - the stars danced playfully in the clear night sky.
etc, etc. If you need more examples, other types of figurative language are symbolism and hyperbole, too. Hope this helps you!