While lying comfortably on a bench, the bar should be lowered to the middle of the chest area, and then back up to full extention without locking your elbows. The lower back should maintain contact with the bench at all times.
Bench press is one of the most talked about measures of strength. While bench press is a 'good' indicator of upper body strength, there are so many other exercises which can demonstrate overall strength (Squats, Leg Press, Deadlift, Hang Cleans). Bench press is a compound exercise.