You Need A Strong Back, Here's Where To Start
Back extensions, if practiced regularly, will help you get rid of round back and discomfort in the spine and will give you a perfect posture. Office workers, or anybody who tends to sit a lot, will find this exercise helpful.
I also find back extensions a key exercise to strengthen your back to execute other exercises (bent over row, stiff-leg deadlift, bent-over lateral raises) with proper form.
Here's how to do one: