An allusion is a type of figurative language. An allusion is a figure of speech - it represents a reference in a text to someone or something outside that text. So, it is figurative language - it's not literal, but rather metaphorical.
An allusion is considered to be figurative language because if you were to write a sentence with an allusion, you are comparing to someone to another person or thing, in which case can sometimes be rude...
