The above is used to tell/order somebody to do something. Note that it should be used only by someone who is older or whose(social) status is higher than the person spoken to. The speaker includes teachers, parents, and older brothers and sisters. The person spoken to includes students, children, and younger brothers and sisters.
テキストの 10ページを 開けなさい。
Open your textbook to p.10.
この えいごの 文を 日本語に ほんやくしなさい。
Translate this English sentence into Japanese.
Lesson 10-1「この くすりを のんで ください。」
Please take this medicine.