Drafting (also known as slipstreaming) is a technique in Mario Kart 64, Mario Kart DS, Mario Kart Wii, and Mario Kart 7 that allows for a short speed boost. In the latter two games, when trailing behind another racer, blue lines appear around the player's kart/bike. If the position is held for about three to five seconds, the player will be surrounded in a blue wind with a modest speed increase. The boost lasts for about three seconds, or until the player hits a wall, obstacle, racer, or item. It can last as long as a Mushroom boost.
In Mario Kart 64, the method is more subtle. There are no lines to indicate if it is being done correctly, the wind is gray instead of blue, and the speed boost is brief.
While tricky to do on curves, this is incredibly useful on straightaways. However, this can be a risky move, as the racer being trailed could pull out an item at any time. It is better to use on CPUs than real racers.