Lures are artificial fishing bait which is designed to attract a fish's attention. It's not considered Bait because it's not intended as fishfood, and is therefore harder to be consumed by any fish.
In Salt, there are many different lures but just one or more are currently craftable. Some are bought, some are quest-rewards, some are gained by looting items and some requires special currencies or quests to be completed before they can be bought.
Most lures in Salt are mostly based on visually be similar to Fly Lures, or "Artificial Flies". Considering that one or more of these lures in Salt are designed to fish in Deep Sea is therefore actually controversial, as such lures in the real world are intended to be used in rivers and shallow waters.
In this page, all ingame lures are listed and categorized by their looks and should not be generalized as "bait".