1993 Nissan 240SX WONT START

I have a 93 nissan 240sx. It has been running fine, until today. I had stopped the car and when I had start it up again it would not turn. The battery seems fine, but when I turn the key all I hear is a clicking sound. All of the indicator lights turn on like they should before start. The interior lights and exterior lights work as well.
I just want an idea of what this might be, maybe an alternator.


THANKS