Bait is a type of Fishing Bait used for catching fish.
Source[]
The Bait recipe is unlocked upon reaching level two in Fishing. The recipe takes 
Bug Meat (1) and produces 5 Bait.
Bait can also be purchased for 
5g from Willy at the Fish Shop, sometimes from the Traveling Cart, grown in a Worm Bin, or obtained from Fishing treasure chests or as a reward from the River Fish Bundle.
Uses[]
To add Bait to a Crab Pot, place the Crab Pot in the water first, then select the Bait and apply it by interacting with the Crab Pot with the Bait active.
Bait reduces the delay before a nibble by 50% when used on a fishing rod. To add Bait to a Fiberglass Rod or Iridium Rod, open the Inventory and interact with the Bait and then interact with the fishing rod. Bait cannot be used on Bamboo Poles. Only one piece of Bait is consumed when applying it to a rod.