How to burn a card?

Also, you can burn your postcard. What is the purpose? To feel yourself powerful!

Hahaha, joke.

What is the real aim?

Honestly, the function “Burn” is only used when you have dozens of duplicates that are put up for sale. If you burn some of the cards, the rest will become unique and hence more valuable. Owing to that, it increases the demand for greeting cards or you can raise their value.
To burn your NFT, click on the triple dot in the postcard window and select "Burn". In the opening window, define the number of postcards you want to get rid of. After that, approve the action by clicking the "Confirm" button. The Metamask extension will open, where you'll also have to accept the operation.
This action is irreversible. After the burning procedure, the copy of your postcard will be deleted and cannot be restored. If you had only one copy of the postcard after burning it, it will vanish from the "Owned" tab of your profile.