信封是人们用来装信件的纸袋
Envelope is a paper pocket,which people put their letter in it
首先我们要写一封信 然后把它装到信封里 最后把它放进邮筒邮递出去
First I am going to write a letter,and then put it in an envelope,finally,put it in the post box and send it away.
很乐意能够帮到你,希望会对你有助.