It is a label, usually printed on paper, although some have been embossed into foil ,, etc. which is used to prepay postage by affixing it onto a letter or other piece to be mailed.
The easiest way is to get what is called 'kiloware' large packets of stamps on paper available through many stamp dealers. Most companies will sell these packets at a reasonable price. You can also...
Save the Children Guide Dogs for the Blind Help The Aged Royal National Institute for Blind Check before sending them if they still accept them in your country. At one time these charities accepted...