You’ve been told that a performance camshaft will give you better performance from your car’s engine. The camshaft is the internal engine component that indirectly controls the opening and closing of the intake and exhaust valves. The camshaft has oblong sections which manipulate the lifters, the valves or the rocker arms to actuate the valves. These sections are called the lobes. With a performance camshaft, these lobes are just a little more elongated, and the oblongs are just a bit wider. The extra length gives extra lift to the valve, which causes it open farther. The wider lobe keeps the valve open longer, which is called duration. Increased lift and duration allow more fuel and air in, and more exhaust out.
For more info, see How a Throttle Body Spacer Improves Engine Performance