A 
postal card is a typically rectangular piece of thick 
paper or thin 
cardboard intended to write on and be mailed without an 
envelope and at a lower rate than a letter.  It is distinguished by 
stamp collectors[?] from a 
postcard in that the postage is pre-printed on it whereas a postcard requires a 
stamp.  A postal card is issued by a 
stamp-issuing authority[?] (typically a country) whereas a postcard is usually printed by a private company, individual or organisation.
In the Art-world the postcard can also be transferred into an art-object. The artform where this is done is called mail art.
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