Discover how crafting works in Diablo 3
You don't craft items in Diablo 3. That would be silly! No, you craft blacksmiths, who craft your items for you. Why didn't I think of doing that? I could have been rolling in swords by now.
The Blacksmith will take your materials and turn them into stabby-tools for you. You can upgrade his shop (which unfolds into a bigger shop in a flash of brilliant light, just like traditional smithies are inclined to), he can add gem sockets to anything that looks at him funny, and you can even talk to him. You'll get the materials required by breaking down trash loot in the field. That means you'll spend even longer clicking on monsters before you have to return to the surface to glower at shopkeepers. Hooray!