In the left panel, the circles represent the topics found their size represents the how present their associated words are in the corpus.
The distance between them represents a measure of difference which means overlapping circles feature a lot of the same words.
When clicking on a circle the right panel shows the words associated with a topic in ranked order starting with the most important.
The red bar represents how many times a word occurs in a topic, while the blue bar represents how often the term appears in the whole corpus.
Hovering over a word in the right panel changes the size of the circles to show how much that word contributes to each topic.