Battery or Alternative?

What is your question?

While driving to work my ABS light came on. Then my Battery light on. Next the panel functions stop working; the wipers were moving very slow on high speed. My radio went out and the headlights when off. I manage to make it to work; but when I turned off the vechile and tried to start it back up. If got a clicking noise like the battery was dead...What caused this problem. Do I need a new battery or replace the alternative.