car trouble

I have a 95 celica.Stock engine.
Today a while ago, I was going to McDolnald. I was stopped by the traffic guard. Then all of a sudden my car went dead on me. They were also some clicking noise in my engine. I also have notice while i am braking at a stop sign or something. It will want to drop to 0 on my tach.. Before that started happening it was wanting to go over 1rpm as if i was stepping on the gas which i wasnt. What is the problem. Battery?
alternator? somthing?????

Thank you