what does : base() do in a constructor code example

Example: c# superclass constructor

// Create Constructor in superclass
public Vehicle( double speed )
    {
      Speed = speed;
      LicensePlate = Tools.GenerateLicensePlate();
    }

//Original Constructor
class Sedan
  {
    public Sedan(double speed)
    {
      Speed = speed;
      LicensePlate = Tools.GenerateLicensePlate();
      Wheels = 4;
    }

// Remove 'Speed' and 'LicensePlate' from Sedan Constructor
// Add 'class Sedan : Vehicle '
// Add 'public Sedan(double speed) : base(speed)'
  
//New Constructor
class Sedan : Vehicle
  {
    public Sedan(double speed) : base(speed)
    {
      Wheels = 4;
    }
  }