A malfunctioning steering column will interfere with the driver's ability to control the direction of the vehicle when it is in motion. The steering column is just one component in this direction control system that also includes the steering rack, power assist system, tie rods and steering knuckle to name a few. If the steering feels lose, the bushing, bearings or clearance on any of these other components can also be the cause of this feeling of lack of control. The chances of needing a new column are rare unless your vehicle has been in an accident. This component is part of the crush mechanism built into vehicles for protection of the driver.
The steering column itself has many components that are fitted together to form this long tubular shaped device. The main shaft running down the middle is made of tempered steel so it will not twist or become out of shape when pressure is exerted against it by the driver when the steering wheel is turned. The other parts on the steering column are also mostly made of steel but some could be made from a polymer to save weight when they are not load bearing.
If you must replace the steering column then all of the other components mounted to it must be detached from it. This includes the wiring harness that go to all of the switches like the turn signals, lights, cruise control, ignition, and horn to name a few. Your vehicle might also have the transmission shifter on the column, which will have to be removed. Once completed the mounting sleeve holding the steering column to the dash can be loosed and the end of the column can be disconnected at its lower end so it can be pulled out.