The Sentences feature allows one to quickly access all previously flagged sentences and today's flagged sentences. For simplicity sake, the video below shows only the "All My Sentences" section: Pressing the top Play button will automatically play all the flagged sentences. The lower play buttons play the audio of its respective sentence. Finally, pressing the "Detail" button allows you to inspect and learn a single sentence in detail.
Similarly, you can save and practice specific sentences that you are learning today: Today's Sentences. Pressing the "See All" button allows you to quickly test yourself through the "Read", "Listening", and "Write" quiz.
Finally, you can quiz yourself on your ability to read the sentence, write the sentence, and remember the correct pinyin from within the text.