I think you may be asking about how to avoid plagiarism when writing about literature. Plagiarism is using another person's ideas as your own, whether these ideas be written, spoken, or in some cases, implied.
If you are writing about a work of literature and want to discuss a particular passage, you have three choices of how to do this. First, you can write out the passage word for word. If you copy exactly like this, you must enclose the passage in quotation marks and then give the reader some type of notation as to who wrote it and where you found it (either in parenthesis, at the bottom of the page, or at the end of work depending on your teacher's requirements). This says to the reader, "I quoted this part exactly from the text, and here is where I got it!" Another option is to rewrite the passage using different words but keeping the same meaning. You would NOT use quotation marks but would still include the notation above. This says to the reader, "I put this in my own words, but here is who said the original and where you can find it!" Finally you can condense the passage into a shorter form. This is good if you are trying to write about several paragraphs at one time. Again, you do not need to include the quotation marks, but you will need to include the notation.
I hope this helps!