Question

What do you mean by the first day cover according to the third level

Answer 1

Philatelists collect first-day covers on letters. Stamp collectors buy new stamps on the day they are released, paste them on letters, and mail them to their own address; when the letter arrives at their house with the postmark and the date, they save it in their collection. This type of letter is known as a first-day cover. They’re never taken out of the box. They’ve only been preserved.