The Gulp! Minnow is a soft-plastic baitfish body soaked in Berkley's scent formula. The draw is the scent and flavor: a fish that grabs it holds on a beat longer than it would a plain plastic, which buys you time on the hookset. Common sizes are 2 to 3 inches, big enough for trout and panfish without being a mouthful.
Pearl is the all-around color and a strong pick in stained or off-color water; chartreuse adds visibility when the water is dingy; rainbow reads as a generic baitfish. It fishes best in low to normal flow and water from 45 to 70F - cool to moderate, not the dead of winter or the heat of high summer.
Rig it on a small jig head or under a float and work it slow: short hops along the bottom, or a dead-drift through a pool with the scent doing the calling. Let it sit between moves - that pause is where the scent earns its keep.
Important: Gulp! counts as bait under most state regulations because of the scent. It is not legal on artificial-only or fly-only water. Check the regs for the stretch you're fishing before you tie one on.