Grubs were the original soft plastic "swimbait" used by recreational anglers. They were paired with a jighead and steadily retrieved through the water column. The curly tail flattens out and flutters behind the grub body when retrieved imitating bait fish.
While new fishing techniques have incorporated grubs, they are still primarily fished the same way with a jighead and steadily retrieved.
Large grubs, 3-inch and longer, in whites and chartreuse and paired with an 1/8th to 1/2 ounce jighead depending on depth are a favorite option of those targeting temperate bass (striped, hybrid striped and white bass).
This same set-up can be used to target walleye and saugeye along rip rap. Instead of steadily retrieving the grub, the grub is bounced along the bottom during the retrieve.
Grubs, 3-inch and shorter, in natural colors are great in clear water streams for bass and panfish, paired with a 1/32nd to 1/4th ounce jighead depending on water depth, current speed and retrieve style. Typically a 1/8th ounce jighead steadily retrieved at medium speed is perfect for clear water streams in Oklahoma.
Twin tail grubs in natural colors can be paired with a 1/8th to 1/4th ounce jighead and cast downstream into a pool on a clear water stream and jigged upstream along the bottom during the retrieve or steadily retrieved cross-current.