The essay design was approved and the stamp was subsequently printed in black, the color for mourning. While no official documentation has been located saying this was to be a memorial stamp, the circumstances of the event indicate that it could very well be the first American commemorative stamp. A cancellation is any mark used to cancel or obliterate a stamp. It renders the stamp useless for further prepayment of postage. A postmark is any mark applied by the post office to any portion of a letter.
Some philatelists use the terms interchangeably, but it can be seen that they mean different things.
Answer - Engraving is where a design is actually carved, or deeply etched, into a metal plate. Then, in the printing process, ink flows into the crevices of the plate. When the plate is applied under pressure to dampened paper, the ink creates raised lines on the paper, which after drying, can be felt when a fingernail is lightly passed over it. You can perform this same test with a dollar bill, also printed by the engraving process. In photogravure, prints are made from plates having an irregular groundwork, or grain.