Question

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

Answer 1

Answer:

On the day when a new stamp is issued, stamp collectors buy those stamps, stick them on the letters and post them to their own address; when this letter reaches their home with the postmark and the date, they preserve it in their collection. This letter is called a first-day cover. They're never opened.12

Explanation:

Always be brainly

Answer 2

Answer:

First day covers are letters that philatelists collect.

On the day when a new stamp is issued, stamp collectors buy those stamps, stick them on the letters and post them to their own address;

when this letter reaches their home with the postmark and the date, they preserve it in their collection