This mode appears in case you are learning a language with articles.
If you enable the Articles mode, you will be required to write all the articles along with the words. If you don't, they will be filled in automatically.
If you want to learn the articles:
1. Go to the "More" tab.
2. Tap on the "Settings" menu option.
3. Tap on "Course Settings".
4. Enable the "Articles" mode.