Topics can be useful on their own to build the sort of small vignettes with words that are shown in the previous screenshot. These visualizations can be used to navigate a large collection of documents. For example, a website can display the different topics as different word clouds, allowing a user to click through to the documents. In fact, they have been used in just this way to analyze large collections of documents.
However, topics are often just an intermediate tool to another end. Now that we have an estimate for each document of how much of that document comes from each topic, we can compare the documents in topic space. This simply means that instead of comparing word to word, we say that two documents ...