This is the 367th most frequent Japanese word.
ください
"Please" (used to make polite requests).
In this context, ください is used as a polite request to ask for an object.
鉛筆をください。
Please give me a pencil.
Here, ください follows a verb (説明する), making a polite request for an action to be performed.
もう一度説明してください。
Please explain once more.
In this sentence, ください is part of a polite instruction conveyed using humble language.