Often you will want to give an example to show your meaning or you will want to repeat an idea in your conclusion, but you will need a different way to say it.
Generally in English writing we move from a broad idea to a specific point. Importantly we give examples to illustrate our meaning. This is particularly important in Academic writing where the reader expects to see a point and then examples to make your meaning clear. For example, if you are talking about the effects of climate change in the USA, the reader would expect you to give examples such as the possibility that the current Californian drought, Hurricane Katrina or an increase in tornadoes may be a result of climate change. In fact, in your writing you always need to link broad ideas to specific examples.