When do Russian people send postcards? Ответить на вопрос, пожалуйста.

Poscards in Russia is a way to send messages for your relatives, friends and neigbours or every man your know and want to "say hello" in such a form. Poscards are of various types, each of them has its own goals. For example, greeting cards are sent before the holidays (Easter, Christmas, New Year) with the aim to congratulate your relatives with them. A picture-poscard is usually sent from places abroad when youre havind a holiday; it portrays a beautiful view from the place where you are. And the last type is an advertising postcard, which contains some commercial offers.