A cause and effect essay explains why something happens. A good essay will make a clear link between the cause and the effect. It will have sufficient evidence to back up the claim that one thing causes another.
It is important that a cause and effect essay be well-organized. You need a clear introduction, in which you define the phenomenon (whatever the cause and effect relationship is) and explain the connection between the two. You also need to explain why the relationship is important. Why do we need to know that this thing causes this?
In the body of your essay, you need to explain how the cause forces the effect. When X happens, it leads to Y. Explain how you know this, and support it with evidence. If you are writing an essay on the topic, it is most likely complex. You need to break it into clear parts.
Finally, end with a conclusion that summarizes the relationship between the cause and effect, and describes the importance of it.