That includes the production casing or liner and its cement, the path into the rock (perforations, a screen, or an open hole), the packer and tubing, and the surface valves. It is chosen for the rate, the sand, the pressure, and whether the well will be lifted, fractured, or monitored.
Completing a well is not drilling it. The hole already exists. A completion can be pulled and replaced, which is a workover, without drilling a new wellbore. The productivity of the finished well depends on the reservoir and on the skin the completion left behind.