Paraphrases are sometimes the same length as the source passage, sometimes shorter. Behrens A quotation uses the exact words of the original. To maintain a passage which is particularly well-written. Do not quote facts available in a wide variety of sources, or your own independent ideas or primary research. Obviously, you must know the audience.
Common knowledge can be facts or interpretations.
Oddly, commonly known facts do not have to be known exactly. For example, the typical adult with a university degree would probably know that George Bernard Shaw was an English playwright who lived around the turn of the century. The other reason you would not have to acknowledge a source here is that the information is readily available in all sorts of reference books. It is difficult for someone new to an academic topic to discover what is common knowledge, for not only must everyone in the discussion know the fact or opinion, but they must know that everyone knows. If your readers are likely to question where you got the idea from, cite the source.