We must first understand what a quotation is. Citation refers to proverbs, data and famous sayings quoted by the author in order to express or prove his point of view more clearly. In order to maintain its authenticity and accuracy, it is not allowed to change or take it out of context at will.

English is similar, but more formal. English quotation is divided into two parts: direct quotation and indirect quotation.

Needless to say, direct speech is the part enclosed in quotation marks, which cannot be changed at all, including tense, semantics, synonyms and so on. Usually can be used as subject, object, complement, attribute, etc. In a sentence, but it is more used as an object, without any restrictions.

Indirect speech is the report of direct speech, which will change in tense and synonyms, but its original intention and basic framework cannot be changed, otherwise it will lose the meaning of quotation.

That's about it. I hope it helps.