Every time you take a new rank of this feat, you learn how to craft a number of items that can be created by one or more of the Crafting Lore skills that you are at least Trained in.
The items you can learn how to craft fall into the following categories:
Each time you gain a rank of this feat, you can choose to either learn how to craft all items in one of these categories or learn how to craft 4 specific items chosen from any combination of categories. Learning the formula for an item more than once provides no benefits.
Whenever you gain a new rank of this feat, you can Retrain any prior ranks for free in the process, provided that doing so does not cause you to forget how to make an item; this allows you (for example) to learn how to make 4 items chosen between the Light Aethertech Weapons and Grenades categories with your first rank, and then retrain when you gain a second rank to learn all of the items in both the Light Aethertech Weapons and Grenades categories.
Unlike most Skill Feats, you can choose to take this feat in place of a Combat Feat. It still counts as a Skill Feat if you do so.
If an item has multiple Tiers that it can be crafted at, you can craft it at a maximum Tier equal to your Proficiency with that skill (Trained = 1, Expert = 2, Master = 3, Legendary = 4, etc.).
You can choose to craft lower-Tier items than your maximum, depending on the effect(s) you want and the materials you have access to.