For example:
The direct quotation is: Xiao Ming once said "I want to fly in the blue sky" (the direct quotation is like a novel dialogue, with quotation marks, and the original sentence is moved intact)
Indirect quotation: Xiaoming once said that he would fly in the blue sky. Indirect speech is equivalent to paraphrasing what Xiao Ming said in the speaker's own way. Without quotation marks, it becomes a narrative in others' mouths.
When writing an article, deliberately quote idioms, poems, aphorisms, allusions, etc. To express their thoughts and feelings, and explain their views on new problems and new principles. This rhetorical device is called quotation.
The function of quotation is to make the argument conclusive, convincing and enlightening, and the language is concise, implicit and elegant.