The Forge is used to craft gear for characters using resources. For example, Wizard's Hat costs 9,630 11,220 and 30 however, it will take the Forge 3 days and 10 hours to craft this item. The player can only Craft one item at a time, perhaps if your is high enough you can.
Leveling up the Forge reduces the time it takes to make items, and also allows new gear to be crafted.
This is what's available in a Level 3 Forge, there will be more available in a Level 4 and higher.