1Please (give me) — a polite request for something; the (irregular) imperative form of the honorific verb くださる.
水をください。
Please give me some water.
この資料を一部くださいませんか？
Could you give me a copy of this document, please?
すみませんが、メニューをください。
Excuse me, could I have a menu, please?
2Please (do ...) — attached after the te-form of a verb (or an honorific-prefixed noun) to politely request an action.
窓を開けてください。
Please open the window.
どうぞお入りください。
Please come in.
名前と電話番号を書いてください。
Please write your name and phone number.