The crafting system is a fun concept in Hearthstone where you can create or disenchant cards and this feature can be accessed in the my collection section of the game.
Crafting consumes Arcane Dust to make new cards that will hopefully make a players deck better, while disenchanting allows players to destroy unwanted cards, granting a quantity of Arcane Dust in exchange. Crafting is the quickest and most direct way of obtaining a specific card, provided you have sufficient Dust.
The amount of Dust necessary to craft is determined by the rarity of the card.
The ability to disenchant your cards to create Arcane Dust in order to then craft stronger cards is essential to building a bigger better deck.
Players are only allowed to have 2 of any card in a deck (and only 1 of each legendary card), so this makes disenchanting your duplicate cards a smart idea to increase the amount of dust you have. because of how strong crafted cards are as a player your goal should be to get as many cards as you can to disenchant.
Crafting and Disenchanting