sounds like your alternator has failed, but before you blame it on the alternator, check the connection at the battery and the alternator, then check the condition of the main red cable that goes to the alternator. then check the tension of the alternator belt, it shoul have hardly any travel.

next, check the connections at the stering wheel end and the thin cable on the solionoid (on the starter).

if all of this fails, jump start (or push start the car) and get a propper test meter, connect this to the alternator, slowly bring the revs up on the engine (the volts should peak between 13 and 14 volts on a healthy engine)

if the voltage is low, replace the alternator.