The "常用英文-國小畢業必學300單字" app is a free educational tool designed for Android users. The app is developed by DavyZhen Dong and belongs to the Education & Reference category. The app's purpose is to help users learn English words in a systematic way. The app includes a set of 300 basic English words that are essential for primary school graduates to learn. The app makers suggest that users should start with these basic words and then gradually move to the more advanced 1000 words for middle school and 3000 words for high school. This approach helps users to learn words more efficiently and effectively. The app is part of a series of free English learning apps, including "英文常用句300句," "聽廣播學英文," and "出國必備旅遊英文APP." The app is developed by the team at 東大資訊工作室. For additional information, users can visit the "常用英文" blog or join the app's Facebook group.