A postcard or post card is a rectangular piece of thick paper or thin cardboard intended for writing and mailing without an envelope and at a lower rate than a letter. Stamp collectors distinguish between postcards (which require a stamp) and...

An envelope is a packaging product, usually made of flat, planar material such as paper or cardboard, and designed to contain a flat object, which in a postal-service context is usually a letter or card. The traditional type is made from a sheet of...