From the fields list, you can see how many of the documents in the documents table contain a particular field, what the top 5 values are, and what percentage of documents contain each value.
You can visualize data in various ways. You can only apply the quick visualize to aggregatable fields. You can visualize the keyword fields, and they are available in the side bar if you uncheck "Hide missing fields".
To view field data statistics, click the name of a field in the fields list.