1997 Plymouth Neon battery light on

1997 Plymouth Neon 4 Cylinder SOHC mileage: 81,000. When I started my car today the lights are dim, but my car still started. On the drive to work when I was stopped at a light, the idle was rough and my battery light came on. I still got to work. & However, when I went to start it again after work it took a few seconds for the radio to come on. My car would not start and my lights were extremely dim. When I got a jump I was able to get home fine, but my lights flickered all the way home even when I pressed on the gas. Now it will not start without a jump. What is my problem? Please help!