Contrary to what many people believe, the best writing is not always long. In fact, the best writing should be concise and meaningful. Redundant language is one of the primary reasons that student writing tends to be longer than needed.
Redundant language occurs when a writer includes information that is unnecessary because it has either already been stated directly, or it is understood based on the other words used.
In the first case, students repeat information they have already included elsewhere. For example, if you mentioned in your introduction that The Color Purple is a novel, it is not necessary to state that the text is a novel again, as in the sentence "In the novel The Color Purple, another cause of pain is unrequited love." The reader is already aware from your introduction that The Color Purple is a novel, so including the information in a subsequent paragraph is considered redundant.
A harder form of redundancy to identify is a pleonasm. This redundancy error is caused when a word is made redundant by the meaning of other words in a sentence or phrase. For example, the term "added bonus" is a pleonasm because a bonus is, by definition, an added element. It is enough to say that something is a "bonus." In another example, saying "end result" includes redundant language because a result comes at the end. It is enough to say that something is "a result" without including the "end."
Other common examples include "future plans," "repeat again," "possibly might," "join together," "honest truth," "unexpected surprise," and "temper tantrum," among others.