Most essays entail analysis - close, careful study of a particular topic or issue.
There are many different ways to analyze, such as classifying, comparing and contrasting, explaining causes and effects, exploring a topic's history or background, or describing a process. In fact, all these different methods of analysis can work to produce entire essays on their own. Sometimes your instructor will ask you to take a stand on a controversial issue and argue your position. For an essay like that, you may be required to synthesize information from various sources in order to support your argument, or to explain a particular part of your subject. Rather, most essays require several different types of analysis.