Cách sử dụng
An envelope is a flat paper container used to put a letter or document inside. You will use an envelope when you want to send a letter or document through the mail. You write the recipient's address on the front of the envelope, put the letter or document inside, seal it, and add a stamp to send it through the mail. Envelopes come in different sizes depending on what you are sending. They can be made of different materials like paper or plastic.