Hop (jump)

From the Super Mario Wiki

The ability to Hop (referred to as Mini-Jump in Mario Kart Super Circuit) is exclusive to Karts. It has been used in all of the Mario Kart series games, excluding Mario Kart: Double Dash!!. Drivers can use this to their advantage, as it chains to a Drift and Hops over small gaps. All drivers can use the Hop by pressing R, and Hopping in Mario Kart 64 can access huge shortcuts. (These shortcuts are the most likely reason for Nintendo taking the Hop out of Mario Kart: Double Dash!!.)

Also, the driver can execute a better jump with the help of a Mushroom or Starman. This technique can be used to get over a pit or chasm.