JEI, or Just Enough Items, is a utility mod made by mezz. Based off of NEI, JEI modifies the existing Inventory GUI by adding an icon list of items to the far right. This list can be searched via a text box at the bottom. This list is useful for checking recipes and uses for items, and can also be used to search for items in opened GUIs. JEI has a lot of addons, generally adding extra modded recipe support like Thaumic JEI.