Distance between the center line of the front wheels and the center line of the rear wheels. Adjusting this value can influence road performance to a considerable degree. For example, the wheelbase can be altered by changing the construction of the suspension arms or by inserting a distancing piece between the engine and the gearbox.
Longer wheel base is better for straits and long fast corners. With this adjustements you can improve aerodynamics of the car. Long wheelbase car is not so suitable for fast cornering.
Shorter wheelbase car have improved drivability, can allow fast cornering, but can suffer a small aerodynamic problems. Designers have to find right compromise, as always.
The cars layout (length over all) is the length of the all major components (monocoque, fuel tank, engine, gearbox) and their relationship to each other. The net total of these lengths dictates, at some extent, the cars wheelbase. Although influent to drivebility, wheel base is not a critical design factor. Shorter cars do not intrinsically have better abilities in corners. Instead wheelbase length is largely a factor driven by the aerodynamicist’s desire for shape to package the sidepods and turning vanes. Layout is critical in other respects; the fuel tank length, gearbox length and engine position all have an effect of the shape and packaging of the car as well as the weight distribution.