this quistion answer is can me sing a song
A functional text is a text to fulfill a certain function, such as instruction manual or description of getting somewhere. A dialogue would be too confusing and redundant for this purpose; the best functional text would simply describe the information it needs to provide in a clear manner.
Answer/Explanation:
A figure of speech or rhetorical figure is a word or phrase that entails an intentional deviation from ordinary language use in order to produce a rhetorical effect. A word or phrase used in a non-literal sense for rhetorical or vivid effect.
I think it is an idiom but I might be wrong
Essential, both mean something is very important