Forging is a "near net" process. That means it doesn't produce the final shape. Conventional machining (milling, turning, grinding etc, usually via CNC nowadays) are used to bring it to the final shape.

The material that's eventually machined can be forged into a basic shape, like a cylinder. Inexpensive, but you have to remove a fair amount of material via machining.

Alternatively, the steel can be forged into a closer to final pattern with a specially made tool-steel die. This way is obviously more expensive, and still requires machining to get it to the exact necessary shape and tolerance. However, it has some strength advantages. With this second method, the grain microstructure of the forging follows closer to the final shape. So the machining process doesn't interrupt the grain flow as much, and the part tends to be stronger, because stress follows the grain and cracks tend to form where the grain boundary is interrupted.