The "Active Dictionary" page contains all of the words or phrases that you have added to your "Personal Dictionary". This page will contain all the words that you want to be part of your daily, active vocabulary. In other words, words or phrases that you want to readily use in speech or writing.
As iterated previously, all the words in your active dictionary are split into five, parts of speech sections. If we select the Nouns section for instance, you can study all words that are nouns from your active vocabulary.