The Launch star is a big circle with a star shape inside of it that usually boosts the driver.
Mario Kart WiiIn Mario Kart Wii, a single large Launch Star appears in Rainbow Road, where it acts as a cannon and shoots racers into a rainbow tunnel and through another large Launch Star at the end (the second Launch Star does not launch racers). The design of the railings of this course also has multiple Launch Stars on it.
Mario Kart 7Launch Stars appear on Rainbow Road, with the look they have in Mario Kart Wii. Several of them appear in the last section of the course. If racers are able to use the glider, they can fly into these Launch Stars to get a speed boost and continue gliding through the next ones. If the player touches one when they're not gliding, they can still get a small speed boost.
Mario Kart 8/Deluxe
In N64 Rainbow Road Launch Stars appear as boost panels and in the air where racers can glide through them to get a speed boost. They are white with a slight color changing hue and a gold frame encompasses them. On the race track, the rails are designed of Launch Stars, instead of, in the original appearance, regular forms of stars. They have an unique sound when driven through.